Sunday, April 30, 2006

Here are the answers to yesterday's Cisco practice questions. New questions later tonight!

CCNA:

By default, what traffic is considered "interesting" by a Cisco router?

A. All IP traffic

B. All ICMP traffic

C. All traffic

D. No traffic

E. Traffic defined with the dialer-group command

F. Traffic defined with the dialer-list command

Answer: D. By default, no traffic is considered interesting.


CCNP / BSCI:

Which of the following protocols will not advertise a redistributed route unless a seed metric is expressly assigned during redistribution? Choose all that apply.

A. RIPv1

B. RIPv2

C. OSPF

D. EIGRP

E. ISIS

F. IGRP

Answer: A, B, E, F. Both versions of RIP require this seed metric to be set, along with IGRP and EIGRP.


CCNP / BCMSN:

What command enables VRRP interface tracking?

A. (config-if)# vrrp tracking

B. (config)# vrrp tracking

C. (config-if)# standby 5 track serial0

D. (config) # standby 5 track serial0

E. VRRP doesn't have interface tracking capabilities.

Answer: E. A major drawback of VRRP is that it has no interface tracking capabilities, as HSRP does.

To your Cisco success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Saturday, April 29, 2006

Passing the BSCI exam and earning your CCNP is all about knowing the details, and when it comes to EIGRP SIA routes, there are plenty of details to know. A quick check in a search engine for "troubleshoot SIA" will bring up quite a few matches. Troubleshooting SIA routes is very challenging in that there's no one reason they occur.

View the EIGRP topology table with the show ip eigrp topology command, and you'll see a code next to every successor and feasible successor. A popular misconception is that we want these routes to have an "A" next to them - so they're active. That's what we want, right? Active routes sound good, right?

Well, they sound good, but they're not. If a route shows as Active in the EIGRP topology table, that means that DUAL is currently calculating that route, and it's currently unusable. When a route is Passive ("P), that means it's not being recalculated and it's a usable route.

Generally, a route shown as Active is going to be there for a very short period of time. By the time you repeat the command, hopefully that Active route has gone Passive. Sometimes that doesn't happen, though, and the route becomes SIA - Stuck In Active.

A route becomes SIA when a query goes unanswered for so long that the neighbor relationship is reset. From experience, I can tell you that troubleshooting SIA routes is more of an art form than a science, but there are four main reasons a route becomes SIA:

The link is unidirectional, so the query can't possibly be answered.

The queried router's resources are unavailable, generally due to high CPU utilization.

The queried router's memory is corrupt or otherwise unable to allow the router to answer the query.

The link between the two routers is of low quality, allowing just enough packets through to keep the neighbor relationship intact, but not good enough to allow the replies through.


To sum it up, routes generally become SIA when a neighbor either doesn't answer a query, or either the query or reply took a wrong turn somewhere. I told you it wasn't the easiest thing to troubleshoot!

To your Cisco success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Getting Started With Hot Standby Routing Protocol (HSRP)

A CCNP / BCMSN Exam Tutorial

Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is considered a high-availability network service, since all three have an almost immediate cutover to a secondary path when the primary path is unavailable.

One of the routers will be selected as the primary ("Active", in HSRP terminology), and that primary will handle the routing while the other routers are in standby, ready to handle the load if the primary router becomes unavailable. In this fashion, HSRP ensures a high network uptime, since it routes IP traffic without relying on a single router.

The hosts using HSRP as a gateway don't know the actual IP or MAC addresses of the routers in the group. They're communicating with a pseudorouter, a "virtual router" created by the HSRP configuration. This virtual router will have a virtual MAC and IP adddres as well.

The standby routers aren't just going to be sitting there, though! By configuring multiple HSRP groups on a single interface, HSRP load balancing can be achieved.

Before we get to the more advanced HSRP configuration, we better get a basic one started! We'll be using a two-router topology here, and keep in mind that one or both of these routers could be multilayer switches as well. For ease of reading, I'm going to refer to them only as routers.

R2 and R3 will both be configured to be in standby group 5. The virtual router will have an IP address of 172.12.23.10 /24. All hosts in VLAN 100 should use this address as their default gateway.

R2(config)#interface ethernet0
R2(config-if)#standby 5 ip 172.12.23.10

R3(config)#interface ethernet0
R3(config-if)#standby 5 ip 172.12.23.10

The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and compare results.

R2#show standby
Ethernet0 - Group 5
Local state is Standby, priority 100
Hellotime 3 sec, holdtime 10 sec
Next hello sent in 0.776
Virtual IP address is 172.12.23.10 configured
Active router is 172.12.23.3, priority 100 expires in 9.568
Standby router is local
1 state changes, last state change 00:00:22

R3#show standby
Ethernet0 - Group 5
Local state is Active, priority 100
Hellotime 3 sec, holdtime 10 sec
Next hello sent in 2.592
Virtual IP address is 172.12.23.10 configured
Active router is local
Standby router is 172.12.23.2 expires in 8.020
Virtual mac address is 0000.0c07.ac05
2 state changes, last state change 00:02:08

We can see that R3 has been selected as the Active router ("local state is Active"), the virtual router's IP is 172.12.23.10, and R2 is the standby router.

There are some HSRP values that you'll need to change from time to time. What if we want R2 to be the Active router instead? Can we change the MAC address of the virtual router? I'll answer those questions in the next part of this HSRP tutorial!

To your Cisco success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
To pass the CCNA exam, you have to be able to write and troubleshoot access lists. As you climb the ladder toward the CCNP and CCIE, you'll see more and more uses for ACLs. Therefore, you had better know the basics!

The use of "host" and "any" confuses some newcomers to ACLs, so let's take a look at that first.
It is acceptable to configure a wildcard mask of all ones or all zeroes. A wildcard mask of 0.0.0.0 means the address specified in the ACL line must be matched exactly a wildcard mask of 255.255.255.255 means that all addresses will match the line.

Wildcard masks have the option of using the word host to represent a wildcard mask of 0.0.0.0. Consider a configuration where only packets from IP source 10.1.1.1 should be allowed and all other packets denied. The following ACLs both do that.

R3#conf t
R3(config)#access-list 6 permit 10.1.1.1 0.0.0.0

R3(config)#conf t
R3(config)#access-list 7 permit host 10.1.1.1

The keyword any can be used to represent a wildcard mask of 255.255.255.255.

R3(config)#access-list 15 permit any

Another often overlooked detail is the order of the lines in an ACL. Even in a two- or three-line ACL, the order of the lines in an ACL is vital.

Consider a situation where packets sourced from 172.18.18.0 /24 will be denied, but all others will be permitted. The following ACL would do that.

R3#conf t
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255
R3(config)#access-list 15 permit any

The previous example also illustrates the importance of configuring the ACL with the lines in the correct order to get the desired results. What would be the result if the lines were reversed?

R3#conf t
R3(config)#access-list 15 permit any
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255

If the lines were reversed, traffic from 172.18.18.0 /24 would be matched against the first line of the ACL. The first line is “permit any", meaning all traffic is permitted. The traffic from 172.18.18.0/24 matches that line, the traffic is permitted, and the ACL stops running. The statement denying the traffic from 172.18.18.0 is never run.

The key to writing and troubleshoot access lists is to take just an extra moment to read it over and make sure it's going to do what you intend it to do. It's better to realize your mistake on paper instead of once the ACL's been applied to an interface!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Here are some CCNA and CCNP practice questions to get your Saturday started off right. Look for new articles and tutorials later today!

CCNA:

By default, what traffic is considered "interesting" by a Cisco router?

A. All IP traffic

B. All ICMP traffic

C. All traffic

D. No traffic

E. Traffic defined with the dialer-group command

F. Traffic defined with the dialer-list command


CCNP / BSCI:

Which of the following protocols will not advertise a redistributed route unless a seed metric is expressly assigned during redistribution? Choose all that apply.

A. RIPv1

B. RIPv2

C. OSPF

D. EIGRP

E. ISIS

F. IGRP


CCNP / BCMSN:

What command enabled VRRP interface tracking?

A. (config-if)# vrrp tracking

B. (config)# vrrp tracking

C. (config-if)# standby 5 track serial0

D. (config) # standby 5 track serial0

E. VRRP doesn't have interface tracking capabilities.


See you later today!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Friday, April 28, 2006

Here are the answers to Thursday's CCNA / CCNP practice questions. I'll have some more questions for you later tonight!

Thursday's CCNA And CCNP Practice Questions

CCNA:

Which of the following devices divides a single broadcast domain into smaller broadcast domains with no additional configuration? Choose all that apply.

A. Hubs

B. Repeaters

C. Switches

D. Routers

Answer: D. Only routers do this by default. Switches can divide a broadcast domain, but only with additional configuration (VLANs). Hubs and repeaters work at Layer 1 and are incapable of dividing broadcast domains.


CCNP / BSCI:

In ISIS terminology, what is an intermediate system?

A. An end host

B. A switch

C. A logical group of routers

D. A single router

E. A logical group of hosts

Answer: D. An intermediate system is a single router in ISIS.


CCNP / BCMSN:

The command show standby is used to verify the configuration of what protocol?

A. IRDP

B. HSRP

C. VRRP

D. GLBP

Answer: B. show standby is the "show ip protocols" of HSRP - it shows you everything you'd ever want to know about your HSRP configuration, and maybe a few things you don't want to know! ;)

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Thursday, April 27, 2006

Thursday's CCNA And CCNP Practice Questions

CCNA:

Which of the following devices divides a single broadcast domain into smaller broadcast domains with no additional configuration? Choose all that apply.

A. Hubs

B. Repeaters

C. Switches

D. Routers


CCNP / BSCI:

In ISIS terminology, what is an intermediate system?

A. An end host

B. A switch

C. A logical group of routers

D. A single router

E. A logical group of hosts


CCNP / BCMSN:

The command show standby is used to verify the configuration of what protocol?

A. IRDP

B. HSRP

C. VRRP

D. GLBP


Answers tomorrow - see you then!


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Answers To Tuesday's Practice Questions

CCNA:

Which of the following is true of ISDN BRI? Choose all that apply.

A. There are three channels - one b-channel and two d-channels.

B. There are three channels - one d-channel and two b-channels.

C. The d-channel(s) set up the call.

D. The b-channel(s) set up the call.

E. The d-channel(s) carry the data, which can be voice or video.

F. The b-channel(s) carry the data, which can be voice or video.

G. The bandwidth is the same for all three channels.

H. The bandwidth differs between the three channels.

Answer: B, C, F, H. ISDN BRI has one D-channel and two B-channels, the D-channel sets up the call, the B-channels carry the voice and/or video data, and the bandwidth does differ between the three channels.


CCNP / BSCI:

You want an EIGRP-enabled interface, ethernet 0, to receive routing updates but not send them. What is the full command you would enter under the EIGRP process to do so?

Answer: passive-interface ethernet0


CCNP / BCMSN:

Which of the following must be agreed upon between switches running MST to be considered in the same region? Choose three.

A. Revision number

B. MST Autonomous System Number

C. MST Metric Weights

D. MST Region Name

E. MST Instance mapping digest

F. Interface VLAN1 must be on the same subnet

Answer: A, D, E. The revision number, region name, and the digest of the MST Instance - VLAN number mapping must match among routers in the same region.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Wednesday, April 26, 2006

CCNA / CCNP Practice Questions For Wednesday

Answers To Tuesday's Questions Will Be Posted Later Tonight!

CCNA:

Identify the three locations where a router can locate an IOS image during the boot process.

A. Flash

B. TFTP Server

C. FTP Server

D. ROM

E. RAM

F. NVRAM

G. A laptop configured as an IOS Server.


CCNP / BSCI:

One effect of configuring a router as an EIGRP Stub is to prevent it from receiving what kind of traffic?

A. LSAs

B. Hellos

C. DUAL Queries

D. Acks

E. Joins


CCNP / BCMSN

In a multilayer switch, what holds the routing information?

A. The route cache

B. The Attribute Table

C. The MAC Mapping Table

D. The Forwarding Information Base

E. The Adjacency Table


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
My Personal Motivational Library

Anyone who's read my articles knows that I'm very big on planning your success. If you want to drive across the country, you map out a plan to do so; if you want to get a CCNA, CCIE, or accomplish anything else in life, you've got to create a success plan for doing so.

If you've never done so, this can be a little tough at first. I'd like to recommend five of my personal favorite planning and/or motivation books that have helped me create plans for a successful career and life.

Brian Tracy's Goals! is a fantastic book for learning how to create a plan for professional and personal success. I highly recommend it, and you can learn more about this great book and Brian's other products at www.briantracy.com. His books are at amazon.com as well.

Mark Burnett, the creator of Survivor and The Apprentice -- well, you just have to read his story to believe it. You can read about his amazing career in Jump In!.

Donny Deutsch's book Often Wrong, Never In Doubt is quite inspiring for those of us creating our own path to professional success. Well worth a read. Warning: contains sexist content in places. Don't blame me, I didn't write it. :)

Nick Saban is the coach of the Miami Dolphins, and his book How Good Do You Want To Be? will help you break through the restraints that you may have put on your own career and accomplishments. This isn't the typical "sports coach rah rah" book so many successful coaches have written, and I'm sure you'll enjoy it.

I'll finish this list with a second Brian Tracy book, TurboCoach. I've actually bought two copies of this book, because I wore the first one out! There's no better way to achieve your dreams than to create a detailed, written plan for doing so, and this book will definitely help you do so.

So there you are! Whether you're looking for help in creating a study and success plan for your studies, or just a little friendly inspiration, these books are a great way to get what you need to succeed. And then it's up to you!

To your Cisco success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Tuesday, April 25, 2006

Whether you're working on your CCNA or CCNP, Cisco certification exams are the most demanding computer certification exams in the IT field. Cisco exams are not a test of memorization, they're a test of your analytical skills. You'll need to look at configurations and console output and analyze them to identify problems and answer detailed questions. To pass these demanding exams, you've got to truly understand how Cisco routers and switches operate - and the key to doing so is right in front of you.

The debug command.

Of course, there is no single "debug" command. Using IOS Help, you can quickly see that there are hundreds of these debugs, and I want to mention immediately that you should never practice these commands on a production router. This is one major reason you need to get some hands-on experience with Cisco products in a home lab or rack rental. No software program or "simulator" is going to give you the debug practice you need.

Now, why am I so insistent that you use debugs? Because that's how you actually see what's going on. It's not enough to type a frame relay LMI command, you have to be able to see the LMIs being exchanged with "debug frame lmi". You don't want to just type a few network numbers in after enabling RIP, you want to see the routes being advertised along with their metrics with "debug ip rip". The list goes on and on.

By using debugs as part of your CCNA and CCNP studies, you're going beyond just memorizing commands and thinking you understand everything that's happening when you enter a command or two. You move to a higher level of understanding how routers, switches, and protocols work -- and that is the true goal of earning your CCNA and CCNP.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
CCNP / BSCI Exam Tutorial: Using The IP Default Next-Hop Command

Part of the challenge of passing the BSCI exam and earning your CCNP certification is learning that while there are some commands that look almost the same, and seem to do the same thing, they don't! The ip default next-hop command is one such command. There is also an "ip next-hop" command, but the default next-hop command operates differently.

If you set an "ip default next-hop" with a route map, that next-hop will be used ONLY if an explicit path to the destination network is not present in the routing table. An extended ACL must be used here, since a source and destination must be defined.

R2(config)#access-list 150 permit ip host 172.1.1.1 210.1.1.0 0.0.0.255

R2(config)#route-map DEFAULT_NEXT_HOP permit
R2(config-route-map)#match ip address 150
R2(config-route-map)#set ip default next-hop 100.1.1.3

R2(config)#interface e0
R2(config-if)#ip policy route-map DEFAULT_NEXT_HOP

When a packet comes into ethernet0 with a source IP of 172.1.1.1 and is destined for any host on the 210.1.1.0/24 network, the next-hop address will be set to 100.1.1.3 IF there is no entry in the routing table for that network.

That's a big "if" - so be careful!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNP Exam / BCMSN Exam Tutorial: DiffServ And Integrated Services

To pass the CCNP exams, you’ve got to master Quality of Service, and the first step in doing so is knowing the differences between the different QoS types.

Now this being Cisco, we can't just have one kind of QoS! We've got best-effort delivery, Integrated Services, and Differentiated Services. Let's take a quick look at all three.

Best-effort is just what it sounds like - routers and switches making their "best effort" to deliver data. This is considered QoS, but it's kind of a "default QoS". Best effort is strictly "first in, first out" (FIFO).

An entire path from Point A to Point B will be defined in advance when Integrated Services are in effect. Integrated Services is much like the High-Occupancy Vehicle lanes found in many larger cities. If your car has three or more people in it, you're considered a "priority vehicle" and you can drive in a special lane with much less congestion than regular lanes. Integrated Services will create this lane in advance for "priority traffic", and when that traffic comes along, the path already exists. Integrated Services uses the Resource Reservation Protocol (RSVP) to create these paths. RSVP guarantees a quality rate of service, since this "priority path" is created in advance.

Integrated Services is defined in RFC 1613. Use your favorite search engine to locate a copy online and read more about this topic. It's a good idea to get into the habit of reading RFCs!

Of course, if you've got a lot of different dedicated paths being created that may or not be used very often, that's a lot of wasted bandwidth. That leads us to the third QoS model, the Differentiated Services model. Generally referred to as DiffServ, there are no advance path reservations and there's no RSVP. The QoS policies are written on the routers and switches, and they take action dynamically as needed. Since each router and switch can have a different QoS policy, DiffServ takes effect on a per-hop basis rather than the per-flow basis of Integrated Services. A packet can be considered "high priority" by one router and "normal priority" by the next.

Believe me, this is just the beginning when it comes to Quality of Service. It's a huge topic on your exams and in the real world's production networks, and as with all other Cisco topics, just master the fundamentals and build from there - and you're on your way to CCNP exam success!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNA Exam Tutorial: Configuring Dialer Profiles

The most common method of configuring ISDN is with dialer maps, but dial information can also be configured on a logical interface. To pass the CCNA exam, you must know how to configure and troubleshoot both dialer maps and dialer profiles.


Dialer Profiles allow different dialing information to be configured onto logical interfaces. The logical interfaces may have different dialing destinations, different remote router names, etc., but they’ll be using the same physical interface.


Dialer strings are used on dialer profiles. Note that each logical interface has a different IP address, a different remote router to dial, and a different dialer string, but they will be using the same physical interface to dial out. The commands dialer pool and dialer pool-member are used to link the logical and physical interfaces. The number following each command must match for the logical interface to correctly bind to the physical interface.


R1(config)#interface dialer0

R1(config-if)#ip address 172.16.1.1 255.255.255.0

R1(config-if)#encapsulation ppp

<. The encapsulation type is placed on both the logical and physical interfaces. >

R1(config-if)#dialer remote-name Remote0



R1(config-if)#dialer pool 1

<>

R1(config-if)#dialer string 5551212

<>

R1(config-if)#dialer-group 1

<>


R1(config)#interface dialer1

R1(config-if)#ip address 172.16.1.2 255.255.255.0

R1(config-if)#encapsulation ppp

R1(config-if)#dialer remote-name Remote1

R1(config-if)#dialer pool 1

R1(config-if)#dialer string 5551234

R1(config-if)#dialer-group 1


R1(config)#interface bri0

R1(config-if)#no ip address

<>

R1(config-if)#encapsulation ppp

<>

R1(config-if)#dialer pool-member 1

<>

R1(config-if)#isdn spid1 0835866101

R1(config-if)#isdn spid2 0835866301




When configuring dialer profiles, the encapsulation type should be placed on both the physical BRI interface and the logical dialer interfaces. The SPIDs are configured on the physical interface as well.


Configuring dialer profiles can be a little tricky at first, and the best way to master this skill is to get real hands-on practice in your own CCNA / CCNP home lab or a rack rental service. Either way, hands-on is the best practice. Best of luck in your CCNA studies!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Tuesday's CCNA And CCNP Practice Questions

The blog's back up, so look for new questions every day!

CCNA:

Which of the following is true of ISDN BRI? Choose all that apply.

A. There are three channels - one b-channel and two d-channels.

B. There are three channels - one d-channel and two b-channels.

C. The d-channel(s) set up the call.

D. The b-channel(s) set up the call.

E. The d-channel(s) carry the data, which can be voice or video.

F. The b-channel(s) carry the data, which can be voice or video.

G. The bandwidth is the same for all three channels.

H. The bandwidth differs between the three channels.


CCNP / BSCI:

You want an EIGRP-enabled interface, ethernet 0, to receive routing updates but not send them. What is the full command you would enter under the EIGRP process to do so?


CCNP / BCMSN:

Which of the following must be agreed upon between switches running MST to be considered in the same region? Choose three.

A. Revision number

B. MST Autonomous System Number

C. MST Metric Weights

D. MST Region Name

E. MST Instance mapping digest

F. Interface VLAN1 must be on the same subnet


Chris Bryant
CCIE #12932
www.thebryantadvantage.com

Monday, April 24, 2006

Cisco CCNP / BCMSN Exam Tutorial: Getting Started With QoS Policies

QoS - Quality of Service - is a huge topic on both the BCMSN exam and real-world networks. QoS is so big today that Cisco's created separate specialist certifications that cover nothing but QoS! It can be an overwhelming topic at first, but master the fundamentals and you're on your way to exam and job success.

If you work with QoS at any level - and sooner or later, you will - you've got to know how to write and apply QoS policies.

Creating and applying such a policy is a three-step process.

Create a QoS class to identify the traffic that will be affected by the policy.

Create a QoS policy containing the actions to be taken by traffic identified by the class.

Apply the policy to the appropriate interfaces.


If the phrase "identify the traffic" sounds like it's time to write an access-list, you're right! Writing an ACL is one of two ways to classify traffic, and is the more common of the two. Before we get to the less-common method, let's take a look at how to use an ACL to classify traffic.

You can use either a standard or extended ACL with QoS policies. The ACL will be written separately, and then called from the class map.

SW1(config)#access-list 105 permit tcp any any eq 80

SW1(config)#class-map WEBTRAFFIC

SW1(config-cmap)#match access-group 105

Now that we've identified the traffic to be affected by the policy, we better get around to writing the policy! QoS policies are configured with the policy-map command, and each clause of the policy will contain an action to be taken to traffic matching that clause.

SW1(config)#policy-map LIMIT_WEBTRAFFIC_BANDWIDTH

SW1(config-pmap)#class WEBTRAFFIC

SW1(config-pmap-c)#police 5000000 exceed-action drop

SW1(config-pmap-c)#exit

This is a simple policy, but it illustrates the logic of QoS policies. The policy map LIMIT_WEBTRAFFIC_BANDWIDTH calls the map-class WEBTRAFFIC. We already know that all WWW traffic will match that map class, so any WWW traffic that exceeds the stated bandwidth limitation will be dropped.

Finally, apply the policy to the appropriate interface.

SW1(config-if)#service-policy LIMIT_WEBTRAFFIC_BANDWIDTH in

Getting your CCNP is a great way to boost your career, and learning QoS is a tremendous addition to your skill set. Like I said, learn the fundamentals, don't get overwhelmed by looking at QoS as a whole, and you're on your way to success!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNP / BSCI Tutorial: Comparing IRDP and HSRP

To pass the BSCI exam, you need to know the difference between IRDP and HSRP. While they have the same basic function, the operation and configuration of each are totally different.

The aim of both is to allow hosts to quickly discover a standby router when the primary router fails. IRDP is commonly used by Windows DHCP clients and several Unix variations, but you do see it in Cisco routers as well. IRDP is defined in RFC 1256.

IRDP (ICMP Router Discovery Protocol) routers will multicast Hello messages that host devices hear. If a host hears from more than one IRDP router, it will choose one as its primary and will start using the other router if the primary it's chosen goes down.

HSRP (Hot Standby Routing Protocol) is a Cisco-proprietary protocol that is designed for quick cutover to a secondary router if the primary fails, but the host devices don't "see" either the primary or secondary router. The hosts use a virtual router as their default gateway. This virtual router has its own IP and MAC address! All the while, the router chosen as the primary is actually the one doing the routing. If the primary router goes down, the secondary router quickly takes over with no major interruption to network services.

The HSRP routers communicate by multicasting updates to 224.0.0.2, and its through these hellos that the HSRP routers decide which router is primary and which is secondary. HSRP is defined in RFC 2281.

The configuration of each of these will be covered in a future tutorial. In the meantime, I urge you to read the RFCs mentioned in this article, and visit www.cisco.com/univercd to read about the configurations and options available for both of these vital protocols.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNA Certification Tutorial: Frame Relay DLCIs - How To Map 'Em And Use 'Em

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we're going to examine what DLCIs do and how they're mapped on a Cisco router.

Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced "del-see") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination.

DLCIs have local significance only. DLCI numbers are not advertised to other routers, and other routers can use the same DLCI numbers without causing connectivity issues.

Cisco uses the term global addressing to describe a technique by which a router in a frame relay network is reached via the same DLCI number from each router in the network. For example, in a 25-router network, the same DLCI number would be used to reach “Router A” by each router.

Global Addressing is an organizational tool that does not affect the fact that DLCIs have local significance only.

The locally significant DLCI must be mapped to the destination router’s IP address. There are two options for this, Inverse ARP and static mapping.

In both of the following examples, the single physical Serial interface on Router 1 is configured with two logical connections through the frame relay cloud, one to Router 2 and one to Router 3.

Inverse ARP runs by default once Frame Relay is enabled, and starts working as soon as you open the interface. By running show frame-relay map after enabling Frame Relay, two dynamic mappings are shown on this router. If a dynamic mapping is shown, Inverse ARP performed it.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), dynamic,

broadcast,, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), dynamic,

broadcast,, status defined, active


Static mappings require the use of a frame map statement. To use static mappings, turn Inverse ARP off with the no frame-relay inverse-arp statement, and configure a frame map statement for each remote destination that maps the local DLCI to the remote IP address. Frame Relay requires the broadcast keyword to send broadcasts to the remote device.

R1#conf t

R1(config)#interface serial0

R1(config-if)#no frame-relay inverse-arp

R1(config-if)#frame map ip 200.1.1.2 122 broadcast

R1(config-if)#frame map ip 200.1.1.3 123 broadcast


The syntax of the frame map statement maps the remote IP address to the local DLCI.
Broadcasts will not be transmitted by default; the broadcast option must be configured.


R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), static,

broadcast,

CISCO, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), static,

broadcast,

CISCO, status defined, active

Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you'll truly master the concepts shown here - and then you're on your way to the CCNA and becoming a master network engineer.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNA Tutorial: Frame Relay DLCIs And Mapping

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we're going to examine what DLCIs do and how they're mapped on a Cisco router.

Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced "del-see") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination.

DLCIs have local significance only. DLCI numbers are not advertised to other routers, and other routers can use the same DLCI numbers without causing connectivity issues.

Cisco uses the term global addressing to describe a technique by which a router in a frame relay network is reached via the same DLCI number from each router in the network. For example, in a 25-router network, the same DLCI number would be used to reach “Router A” by each router.

Global Addressing is an organizational tool that does not affect the fact that DLCIs have local significance only.

The locally significant DLCI must be mapped to the destination router’s IP address. There are two options for this, Inverse ARP and static mapping.

In both of the following examples, the single physical Serial interface on Router 1 is configured with two logical connections through the frame relay cloud, one to Router 2 and one to Router 3.

Inverse ARP runs by default once Frame Relay is enabled, and starts working as soon as you open the interface. By running show frame-relay map after enabling Frame Relay, two dynamic mappings are shown on this router. If a dynamic mapping is shown, Inverse ARP performed it.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), dynamic,

broadcast,, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), dynamic,

broadcast,, status defined, active


Static mappings require the use of a frame map statement. To use static mappings, turn Inverse ARP off with the no frame-relay inverse-arp statement, and configure a frame map statement for each remote destination that maps the local DLCI to the remote IP address. Frame Relay requires the broadcast keyword to send broadcasts to the remote device.

R1#conf t

R1(config)#interface serial0

R1(config-if)#no frame-relay inverse-arp

R1(config-if)#frame map ip 200.1.1.2 122 broadcast

R1(config-if)#frame map ip 200.1.1.3 123 broadcast


The syntax of the frame map statement maps the remote IP address to the local DLCI.
Broadcasts will not be transmitted by default; the broadcast option must be configured.


R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), static,

broadcast,

CISCO, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), static,

broadcast,

CISCO, status defined, active

Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you'll truly master the concepts shown here - and then you're on your way to the CCNA and becoming a master network engineer.
CCNA Certification Exam Tutorial: Frame Relay DLCIs And Mapping

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we're going to examine what DLCIs do and how they're mapped on a Cisco router.

Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced "del-see") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination.

DLCIs have local significance only. DLCI numbers are not advertised to other routers, and other routers can use the same DLCI numbers without causing connectivity issues.

Cisco uses the term global addressing to describe a technique by which a router in a frame relay network is reached via the same DLCI number from each router in the network. For example, in a 25-router network, the same DLCI number would be used to reach “Router A” by each router.

Global Addressing is an organizational tool that does not affect the fact that DLCIs have local significance only.

The locally significant DLCI must be mapped to the destination router’s IP address. There are two options for this, Inverse ARP and static mapping.

In both of the following examples, the single physical Serial interface on Router 1 is configured with two logical connections through the frame relay cloud, one to Router 2 and one to Router 3.

Inverse ARP runs by default once Frame Relay is enabled, and starts working as soon as you open the interface. By running show frame-relay map after enabling Frame Relay, two dynamic mappings are shown on this router. If a dynamic mapping is shown, Inverse ARP performed it.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), dynamic,

broadcast,, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), dynamic,

broadcast,, status defined, active


Static mappings require the use of a frame map statement. To use static mappings, turn Inverse ARP off with the no frame-relay inverse-arp statement, and configure a frame map statement for each remote destination that maps the local DLCI to the remote IP address. Frame Relay requires the broadcast keyword to send broadcasts to the remote device.

R1#conf t

R1(config)#interface serial0

R1(config-if)#no frame-relay inverse-arp

R1(config-if)#frame map ip 200.1.1.2 122 broadcast

R1(config-if)#frame map ip 200.1.1.3 123 broadcast


The syntax of the frame map statement maps the remote IP address to the local DLCI.
Broadcasts will not be transmitted by default; the broadcast option must be configured.


R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), static,

broadcast,

CISCO, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), static,

broadcast,

CISCO, status defined, active

Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you'll truly master the concepts shown here - and then you're on your way to the CCNA and becoming a master network engineer.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com


Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you'll truly master the concepts shown here - and then you're on your way to the CCNA and becoming a master network engineer.
Learning The Basics Of Frame Relay DLCIs

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we're going to examine what DLCIs do and how they're mapped on a Cisco router.

Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced "del-see") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination.

DLCIs have local significance only. DLCI numbers are not advertised to other routers, and other routers can use the same DLCI numbers without causing connectivity issues.

Cisco uses the term global addressing to describe a technique by which a router in a frame relay network is reached via the same DLCI number from each router in the network. For example, in a 25-router network, the same DLCI number would be used to reach “Router A” by each router.

Global Addressing is an organizational tool that does not affect the fact that DLCIs have local significance only.

The locally significant DLCI must be mapped to the destination router’s IP address. There are two options for this, Inverse ARP and static mapping.

In both of the following examples, the single physical Serial interface on Router 1 is configured with two logical connections through the frame relay cloud, one to Router 2 and one to Router 3.

Inverse ARP runs by default once Frame Relay is enabled, and starts working as soon as you open the interface. By running show frame-relay map after enabling Frame Relay, two dynamic mappings are shown on this router. If a dynamic mapping is shown, Inverse ARP performed it.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), dynamic,

broadcast,, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), dynamic,

broadcast,, status defined, active


Static mappings require the use of a frame map statement. To use static mappings, turn Inverse ARP off with the no frame-relay inverse-arp statement, and configure a frame map statement for each remote destination that maps the local DLCI to the remote IP address. Frame Relay requires the broadcast keyword to send broadcasts to the remote device.

R1#conf t

R1(config)#interface serial0

R1(config-if)#no frame-relay inverse-arp

R1(config-if)#frame map ip 200.1.1.2 122 broadcast

R1(config-if)#frame map ip 200.1.1.3 123 broadcast


The syntax of the frame map statement maps the remote IP address to the local DLCI.
Broadcasts will not be transmitted by default; the broadcast option must be configured.


R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0x7A,0x1CA0), static,

broadcast, CISCO, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0x7B,0x1CB0), static,

broadcast, CISCO, status defined, active

Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you'll truly master the concepts shown here - and then you're on your way to the CCNA and becoming a master network engineer.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Answers To Saturday's CCNA / CCNP Practice Questions

CCNA:

Which of the following is true of both IGRP and EIGRP? Choose all that apply.

A. They both understand VLSM.

B. They both allow the use of wildcard masks.

C. They both assume a serial interface is connected to a T1 line.

D. They both have topology tables.

E. They both choose successors and feasible successors.

F. They both use broadcasts to send routing updates.

Answer: B, E. Of the two, only EIGRP understands VLSM, allows the use of wildcard masks, and has a topology table. Only IGRP uses broadcasts to send routing updates.

CCNP / BSCI:

What does an IPv6 address beginning with 2002 and carrying a /48 prefix indicate?

A. The address is found on 6to4 tunnel access routers.

B. The address is found on 6to4 tunnel edge routers.

C. The address is a universal loopback address for IPv6.

D. The address is a multicast address for IPv6.

E. The address is a broadcast address for IPv6.

Answer: B. You'll find this address on a 6to4 tunnel edge router.


CCNP / BCMSN:

Which of the following commands applies a QoS policy to an interface?

A. qos-policy

B. service-policy

C. qos enable

D. access-group

E. access-class

Answer: B. The service-policy command is followed by the name of the policy map and the direction in which the policy will be applied (inbound or outbound).

Chris Bryant

CCIE #12933

http://www.thebryantadvantage.com/
Answers To Saturday's CCNA / CCNP Practice Questions

CCNA:

Which of the following is true of both IGRP and EIGRP? Choose all that apply.

A. They both understand VLSM.

B. They both allow the use of wildcard masks.

C. They both assume a serial interface is connected to a T1 line.

D. They both have topology tables.

E. They both choose successors and feasible successors.

F. They both use broadcasts to send routing updates.

Answer: C, E. Of the two, only EIGRP understands VLSM, allows the use of wildcard masks, and has a topology table. Only IGRP uses broadcasts to send routing updates.


CCNP / BSCI:

What does an IPv6 address beginning with 2002 and carrying a /48 prefix indicate?

A. The address is found on 6to4 tunnel access routers.

B. The address is found on 6to4 tunnel edge routers.

C. The address is a universal loopback address for IPv6.

D. The address is a multicast address for IPv6.

E. The address is a broadcast address for IPv6.

ANSWER: This is an address you'll find on a 6to4 tunnel edge router.


CCNP / BCMSN:

Which of the following commands applies a QoS policy to an interface?

A. qos-policy

B. service-policy

C. qos enable

D. access-group

E. access-class

Answer: B. The service-policy command is followed by the name of the policy and the direction in which the policy will be applied.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Saturday, April 22, 2006

Saturday's CCNA / CCNP Practice Questions

I apologize for the lack of questions yesterday!

CCNA:

Which of the following is true of both IGRP and EIGRP? Choose all that apply.

A. They both understand VLSM.

B. They both allow the use of wildcard masks.

C. They both assume a serial interface is connected to a T1 line.

D. They both have topology tables.

E. They both choose successors and feasible successors.

F. They both use broadcasts to send routing updates.


CCNP / BSCI:

What does an IPv6 address beginning with 2002 and carrying a /48 prefix indicate?

A. The address is found on 6to4 tunnel access routers.

B. The address is found on 6to4 tunnel edge routers.

C. The address is a universal loopback address for IPv6.

D. The address is a multicast address for IPv6.

E. The address is a broadcast address for IPv6.


CCNP / BCMSN:

Which of the following commands applies a QoS policy to an interface?

A. qos-policy

B. service-policy

C. qos enable

D. access-group

E. access-class


Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Thursday, April 20, 2006

Here are the answers to the bonus questions I posted Wednesday.

CCNA:

What protocol uses the term cost to describe its metric?


A. OSPF

B. IGRP

C. EIGRP

D. RIPv1

E. RIPv2

Answer: B. OSPF refers to its metric as "cost".


CCNP / BSCI:

Which of the following phrases applies to the distribution layer of Cisco's three-layer networking model?

A. traffic filtering generally occurs here

B. end users interact with the network here

C. Internet access is granted here

D. traffic filtering should be avoided at this layer

Answer: A, C. Traffic filtering and internet access generally occur at the distribution layer of Cisco's three-layer model. Traffic filtering should be avoided at the core layer to spare core devices any unnecessary latency.


CCNP / BCMSN:

At what layer of the Cisco hierarchical networking model should traffic be classified and marked when appropriate?

A. Access

B. Distribution

C. Classification

D. Core

E. Policing

Answer: A. The classification and marking of traffic for QoS purposes should take place at the access layer - the layer closest to the end users.


Wednesday Morning's CCNA / CCNP Practice

CCNA:

What are the frame relay LMI types? Choose all that apply.

A. cisco

B. ansi

C. dlci

D. isl

E. q933a

F. dot1q

G. hdlc

H. ppp

Answer: A, B, E. Cisco is the default.


CCNP / BSCI:

There are 10 routers in a BGP AS. The number of separate BGP peer connections that would be needed for a full mesh is:

A. 90

B. 60

C. 100

D. 99

E. 45

F. 98

Answer: E. To calculate the number of separate TCP connections you'll need for a logical full mesh in a BGP AS, use this formula:

X (X - 1) / 2
"X" being the number of routers. With 10 routers, the result is 90 / 2, or 45.



CCNP / BCMSN:

A packet enters a multilayer switch with a CoS of 2. Which of the following is true?

A. By default, the CoS value will be trusted.

B. By default, the CoS value will not be trusted.

C. If trusted, the CoS value will map to an internal DSCP value of 2.

D. If trusted, the CoS value will map to an internal DSCP value of 16.

E. If trusted, the CoS value will map to an internal DSCP value of 4.

Answer: B. The default behavior of the switch is to not trust incoming CoS values.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Thursday's CCNA and CCNP Practice Questions

Answers to Wednesday's questions will be posted tonight!

CCNA:

A frame enters a switchport. The destination MAC address is known to the switch. The destination MAC address is found off a different port than the one that received the frame. What word best describes the action the switch will take on the frame?

A. Broadcast

B. Multicast

C. Unicast

D. Dropped

E. Filtered


CCNP / BSCI:

Which of the following EIGRP packet types are considered "unreliable"? Choose all that apply.

A. Hello

B. Ack

C. Update

D. Query

E. Reply


CCNP / BCMSN

The acronym "FIFO" relates to which one of the following QoS methodologies?

A. Best effort

B. Integrated Services

C. Differentiated Services

D. Coded Services


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
CCNP / BSCI Exam Tutorial: Broadcasts And The IP Helper-Address Command

As you know from your CCNA studies, while routers accept and generate broadcasts, they do not forward them. This can be quite a problem when a broadcast needs to get to a device such as a DHCP or TFTP server that's on one side of a router with other subnets on the other side.


If a PC attempts to locate a DNS server with a broadcast, the broadcast will be stopped by the router and will never get to the DNS server. By configuring the ip helper-address command on the router, UDP broadcasts such as this will be translated into a unicast by the router, making the communication possible. The command should be configured on the interface that will be receiving the broadcasts.

R1(config)#int e0
R1(config-if)#ip helper-address ?
A.B.C.D IP destination address

R1(config-if)#ip helper-address 100.1.1.2

Now, you may be wondering if this command covers all UDP services. Sorry, you're not getting off that easy! The command does forward eight common UDP service broadcasts, though.

TIME, port 37

TACACS, port 49

DNS, port 53

BOOTP/DHCP Server, port 67

BOOTP/DHCP Client, port 68

TFTP, port 69

NetBIOS name service, port 137

NetBIOS datagram service, port 138

That's going to cover most scenarios where the ip helper-address command will be useful, but what about those situations where the broadcast you need forwarded is not on this list? You can use the ip forward-protocol command to add any UDP port number to the list.

Additionally, to remove protocols from the default list, use the no ip forward-protocol command. In the following example, we'll add the Network Time Protocol port to the forwarding list while removing the NetBIOS ports. Remember, you can use IOS Help to get a list of commonly filtered ports!

R1(config)#ip forward-protocol udp ?
<0-65535> Port number
biff Biff (mail notification, comsat, 512)
bootpc Bootstrap Protocol (BOOTP) client (68)
bootps Bootstrap Protocol (BOOTP) server (67)
discard Discard (9)
dnsix DNSIX security protocol auditing (195)
domain Domain Name Service (DNS, 53)
echo Echo (7)
isakmp Internet Security Association and Key Management Protocol (500)
mobile-ip Mobile IP registration (434)
nameserver IEN116 name service (obsolete, 42)
netbios-dgm NetBios datagram service (138)
netbios-ns NetBios name service (137)
netbios-ss NetBios session service (139)
ntp Network Time Protocol (123)
pim-auto-rp PIM Auto-RP (496)
rip Routing Information Protocol (router, in.routed, 520)
snmp Simple Network Management Protocol (161)

snmptrap SNMP Traps (162)
sunrpc Sun Remote Procedure Call (111)
syslog System Logger (514)
tacacs TAC Access Control System (49)
talk Talk (517)
tftp Trivial File Transfer Protocol (69)
time Time (37)
who Who service (rwho, 513)
xdmcp X Display Manager Control Protocol (177)


R1(config)#ip forward-protocol udp 123
R1(config)#no ip forward-protocol udp 137
R1(config)#no ip forward-protocol udp 138

As you can see, the ip helper-address command helps work around the fact that broadcasts aren't forwarded by routers by default, and if you just need to send one or two broadcast types, the other types can be turned off easily.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco Home Lab Tutorial - 2501s In Your CCNA / CCNP Home Lab

To be truly prepared for your CCNA and CCNP exams, you need real hands-on experience with real Cisco routers and switches. However, a production network is a really bad place to practice your configurations, but an excellent way to get fired and/or sued. The key to becoming a true CCNA and CCNP is assembling your own Cisco home lab.

You don't have to spend a lot of money to do so; used Cisco equipment is cheaper than ever. It's robust as well - I've bought literally hundreds of used routers and switches over the years and have had very few problems. I owe much of my skill to practicing configurations and troubleshooting in my own home lab.

2501 routers are fantastic for CCNA and CCNP home labs. They come with two serial interfaces, allowing you to connect one interface directly to another router (you'll need a DTE/DCE cable for that, too) while connecting another to a frame relay switch if you like. If you don't have a frame relay switch, you can connect a 2501 directly to two other routers via the serial interfaces.

You also have an AUI port, which requires a transceiver to operate as your Ethernet interface. Transceivers are pretty cheap and readily available from Cisco resellers and ebay vendors, so pick one up for each 2503 you decide to buy.

2501 routers don't come with BRI interfaces, but not every router in your lab has to be ISDN-ready. If you choose not to have ISDN in your lab at all, 2501s are the way to go. If you do want to run ISDN and have an ISDN simulator device, you can get two 2503s and the rest of your routers can be 2501.

All in all, 2501 routers are great for your CCNA / CCNP home lab.
They cost less than $100 each on ebay, so they're also very affordable. There's no better training than training on your own CCNA or CCNP home lab, and you can always sell the equipment later if you like. Basically, you're renting the routers and switches, and the experience you get by working with the real deal is invaluable.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Wednesday, April 19, 2006

Wednesday's CCNA And CCNP Practice Questions - The Second Set Today! :)

CCNA:

What protocol uses the term cost to describe its metric?

A. ISIS

B. OSPF

C. IGRP

D. EIGRP

E. RIPv1

F. RIPv2


CCNP / BSCI:

Which of the following phrases applies to the distribution layer of Cisco's three-layer networking model?

A. traffic filtering generally occurs here

B. end users interact with the network here

C. Internet access is granted here

D. traffic filtering should be avoided at this layer


CCNP / BCMSN:

At what layer of the Cisco hierarchical networking model should traffic be classified and marked when appropriate?

A. Access

B. Distribution

C. Classification

D. Core

E. Policing


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Wednesday Morning's CCNA / CCNP Practice Questions

Two sets of questions today - the second one will be posted this afternoon!

CCNA:

What are the frame relay LMI types? Choose all that apply.

A. cisco

B. ansi

C. dlci

D. isl

E. q933a

F. dot1q

G. hdlc

H. ppp


CCNP / BSCI:

There are 10 routers in a BGP AS. The number of separate BGP peer connections that would be needed for a full mesh is:

A. 90

B. 60

C. 100

D. 99

E. 45

F. 98


CCNP / BCMSN:

A packet enters a multilayer switch with a CoS of 2. Which of the following is true?

A. By default, the CoS value will be trusted.

B. By default, the CoS value will not be trusted.

C. If trusted, the CoS value will map to an internal DSCP value of 2.

D. If trusted, the CoS value will map to an internal DSCP value of 16.

E. If trusted, the CoS value will map to an internal DSCP value of 4.

Tuesday, April 18, 2006

Here are the answers to yesterday's CCNA / CCNP practice questions.

More free questions later tonight!

CCNA:

A RIP router recieves two routing updates for the same network at the exact same time. The metric for one of the routes is higher than the other. What will happen to the update with the higher metric?

A. It will be discarded.

B. It will be put into the routing table.

C. It will be placed into the topology table.

D. It will act as the feasible successor.

Answer: A. The update with the higher metric will be discarded. RIP doesn't use a topology table or a feasible successor.


CCNP / BSCI:

What combination of letters and symbols indicate a RIP route learned via redistribution?

A. R

B. R*

C. R IA

D. R EX

E. R IA*

Answer: A. RIP only has one code for its routes, regardless of how it was learned, and that's an "R".

CCNP / BCMSN:What command will hardcode a 3550 port into switching mode? Short answer, no choices given.

Answer: The interface-level command "switchport" places a 3550 port into switching mode.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
CCNA Home Lab Setup: The 2503 Router

I know from experience that part of the excitement and anxiety of putting together your own CCNA / CCNP home lab is deciding what to buy! While you can make a workable home lab out of almost any combination of Cisco routers and switches, some routers are better suited for home lab work than others because they can fill multiple roles.

When you buy CCNA or CCNP "lab kits" - bundles of routers and switches - you can get a little confused about whether you're getting a good deal. One router I get asked about quite a bit is the 2503.

2503 routers are fantastic for CCNA and CCNP home labs. They come with two serial interfaces, allowing you to connect one interface directly to another router (you'll need a DTE/DCE cable for that, too) while connecting another to a frame relay switch if you like. If you don't have a frame relay switch, you can connect a 2503 directly to two other routers via the serial interfaces.

You also have an AUI port, which requires a transceiver to operate as your Ethernet interface. Transceivers are pretty cheap and readily available from Cisco resellers and ebay vendors, so pick one up for each 2503 you decide to buy.

2503 routers also come with a BRI interface. Even though you may not have an ISDN simulator right now, you may choose to add one later. That makes a 2503 a great bet for future lab expansion.

All in all, 2503 routers are great for your CCNA / CCNP home lab. They run about $125 each on ebay, or less, so they're also very affordable. There's no better training than training on your own CCNA or CCNP home lab, and you can always sell the equipment later if you like. Basically, you're renting the routers and switches, and I can tell you from personal experience that the experience you get by working with the real deal is invaluable.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
CCNP / BCMSN Exam Tutorial: An Introduction To CGMP

If a Layer Two switch doesn't have the capabilities to run IGMP Snooping, it will be able to run CGMP - Cisco Group Membership Protocol. CGMP allows the multicast router to work with the Layer Two switch to eliminate unnecessary multicast forwarding.

CGMP will be enabled on both the multicast router and the switch, but the router's going to do all the work. The router will be sending Join and Leave messages to the switch as needed. PIM must be running on the router interface facing the switch before enabling CGMP, as you can see:

R1(config)#int e0
R1(config-if)#ip cgmp
WARNING: CGMP requires PIM enabled on interface
R1(config-if)#ip pim sparse
R1(config-if)#ip cgmp


When CGMP is first enabled on both the multicast router and switch, the router will send a CGMP Join message, informing the switch that a multicast router is now connected to it. This particular CGMP Join will contain a Group Destination Address (GDA) of 0000.0000.0000 and the MAC address of the sending interface. The GDA is used to identify the multicast group, so when this is set to all zeroes, the switch knows this is an introductory CGMP Join, letting the switch know that the multicast router is online.

The switch makes an entry in its MAC table that this router can be found off the port that the CGMP Join came in on. The router will send a CGMP Join to the switch every minute to serve as a keepalive.

A workstation connected to the switch on port 0/5 now wishes to join multicast group 225.1.1.1. The Join message is sent to the multicast router, but first it will pass through the switch. The switch will do what you'd expect it to do - read the source MAC address and make an entry for it in the MAC address table as being off port fast 0/5 if there's not an entry already there. (Don't forget that the MAC address table is also referred to as the CAM table or the bridging table.)


The router will then receive the Join request, and send a CGMP Join back to the switch. This CGMP Join will contain both the multicast group's MAC address and the requesting host's MAC address. Now the switch knows about the multicast group 225.1.1.1 and that a member of that group is found off port fast 0/5. In the future, when the switch receives frames destined for that multicast group, the switch will not flood the frame as it would an unknown multicast. Instead, the switch will forward a copy of the frame to each port that it knows leads to a member of the multicast group.

Two major benefits of CGMP are the explicit Join and Leave Group messages. In the next part of this BCMSN exam tutorial, we’ll take a look at the Leave Group messages.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Monday, April 17, 2006

Monday's CCNA And CCNP Practice Questions

CCNA:

A RIP router recieves two routing updates for the same network at the exact same time. The metric for one of the routes is higher than the other. What will happen to the update with the higher metric?

A. It will be discarded.

B. It will be put into the routing table.

C. It will be placed into the topology table.

D. It will act as the feasible successor.


CCNP / BSCI:

What combination of letters and symbols indicate a RIP route learned via redistribution?

A. R

B. R*

C. R IA

D. R EX

E. R IA*


CCNP / BCMSN:

What command will hardcode a 3550 port into switching mode? Short answer, no choices given.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Here are the answers to Saturday's CCNA / CCNP Practice Questions.

More free questions coming later tonight!

CCNA:

Identify the true statements regarding an ISDN connection. Choose all that apply.

A. CHAP requires the passwords to be the same on each router.

B. CHAP allows the passwords to be different on each router.

C. CHAP can only run when HDLC is enabled.

D. CHAP can only run when PPP is enabled.

E. CHAP can run on PPP or HDLC.

F. CHAP requires the use of the ppp chap sent-username command.

G. CHAP does not use the ppp chap sent-username command.

Answer: A, D, G. CHAP does require that the password be the same on both involved routers. CHAP cannot run on HDLC and requires PPP. CHAP does not have a sent-username command, only PAP does.


CCNP / BSCI:

Examine the following configuration and identify the true statements.

router bgp 100
neighbor 10.1.1.2 remote-as 200

A. The local router is in AS 100.

B. The local router is in AS 200.

C. The remote router is an iBGP neighbor.

D. The remote router is an eBGP neighbor.

Answer: A, B, D. The local router's AS is in the first line, with the remote router's AS in the second line. Since they're in different Autonomous Systems, they're eBGP neighbors.


CCNP / BCMSN:Which of the following best describes the RPF Check?

A. The RPF check assures that the packet is on the way to the correct destination.

B. The RPF Check assures that the packet is flowing away from the source.

C. The RPF Check assures the router that the packet is indeed a multicast packet.

D. The RPF Check assures the router that the packet is not a broadcast packet.

E. The RPF Check assures the router that the packet is not a multicast packet.

Answer: B. The purpose of the RPF check is to make sure the multicast packet is flowing away from the source.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco CCNA Exam Tutorial: IGRP Unequal-Cost Load Balancing And The Variance Command

To pass the CCNA exam, you've got to know how to work with IGRP and EIGRP unequal-cost load balancing. You may not see much IGRP in production networks anymore, but you'll see a lot of EIGRP, and part of fine-tuning your EIGRP network is making sure that all paths are in use while allowing for varying bandwidth rates.

Using the variance command is the easy part - it's getting the metric that's the hard part with IGRP. With EIGRP, you just look in the topology table and that's it. With IGRP, you've got to run a debug to get the right metric.

The variance command is a multiplier when the value supplied with the variance command is multiplied by the lowest-cost metric, it must exceed the higher-cost metric in order for the higher-cost route to be added.

If that sounds complicated, it's not. It's one of those things that sounds difficult, but isn't. Trust me!

In this example, R1 has two paths to 172.23.0.0, but is currently using only one. By looking in the IP routing table, we've seen that the lowest-cost metric for network 172.23.0.0 on R1 is 8576. This path goes through the 172.12.123.0 network. There is another valid path that uses the 172.12.13.0 network, but is not currently in use.

I 172.23.0.0/16 [100/8576] via 172.12.123.2, 00:00:53, Serial0

IGRP does not have a “show" command that displays all valid routes to a destination, as does EIGRP. The command debug ip igrp transactions will show the current metric of the routes using the 512 KBPS route.

R1#debug ip igrp transactions
IGRP protocol debugging is on
19:17:51: IGRP: broadcasting request on Loopback0
19:17:51: IGRP: broadcasting request on Serial0
19:17:51: IGRP: broadcasting request on Serial1
19:17:51: IGRP: received update from 172.12.13.3 on Serial1
19:17:51: subnet 172.12.13.0, metric 23531 (neighbor 21531)
19:17:51: subnet 172.12.123.0, metric 23531 (neighbor 8476)
19:17:51: network 1.0.0.0, metric 24031 (neighbor 8976)
19:17:51: network 2.0.0.0, metric 22131 (neighbor 1600)
19:17:51: network 3.0.0.0, metric 22031 (neighbor 501)
19:17:51: network 172.23.0.0, metric 21631 (neighbor 1100)

R1(config)#router igrp 1
R1(config-router)#variance 3

R1#show ip route 172.23.0.0
Routing entry for 172.23.0.0/16

Known via "igrp 1", distance 100, metric 8576
Redistributing via igrp 1
Advertised by igrp 1 (self originated)
Last update from 172.12.123.2 on Serial0, 00:00:01 ago
Routing Descriptor Blocks:
* 172.12.13.3, from 172.12.13.3, 00:00:20 ago, via Serial1
Route metric is 21631, traffic share count is 1
Total delay is 21000 microseconds, minimum bandwidth is 512 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0

172.12.123.3, from 172.12.123.3, 00:00:20 ago, via Serial0
Route metric is 8576, traffic share count is 3
Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0

172.12.123.2, from 172.12.123.2, 00:00:01 ago, via Serial0
Route metric is 8576, traffic share count is 3
Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0

The metric for 172.23.0.0 through the direct connection is 21631. A variance of 3 means that any route with a metric less than the best metric multiplied by the variance (in this case, 8576 x 3 = 25728) will be entered into the routing table. R1 now has three unequal-cost paths to 172.23.0.0 in its routing table, and load balancing will take place.

IGRP unequal-cost load balancing takes some practice, but as you can see, once you get the metric it's easy to work with. Just make sure you know how to get that metric!

To your CCNA success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Saturday, April 15, 2006

Saturday's CCNA And CCNP Practice Questions

CCNA:

Identify the true statements regarding an ISDN connection. Choose all that apply.

A. CHAP requires the passwords to be the same on each router.

B. CHAP allows the passwords to be different on each router.

C. CHAP can only run when HDLC is enabled.

D. CHAP can only run when PPP is enabled.

E. CHAP can run on PPP or HDLC.

F. CHAP requires the use of the ppp chap sent-username command.

G. CHAP does not use the ppp chap sent-username command.


CCNP / BSCI:

Examine the following configuration and identify the true statements.

router bgp 100
neighbor 10.1.1.2 remote-as 200

A. The local router is in AS 100.

B. The local router is in AS 200.

C. The remote router is an iBGP neighbor.

D. The remote router is an eBGP neighbor.


CCNP / BCMSN:

Which of the following best describes the RPF Check?

A. The RPF check assures that the packet is on the way to the correct destination.

B. The RPF Check assures that the packet is flowing away from the source.

C. The RPF Check assures the router that the packet is indeed a multicast packet.

D. The RPF Check assures the router that the packet is not a broadcast packet.

E. The RPF Check assures the router that the packet is not a multicast packet.


Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Friday, April 14, 2006

Thursday's CCNA And CCNP Practice Questions

My apologies for these not being online yesterday, but blogger.com was having a little trouble yesterday!

CCNA:

What value serves as a keepalive for frame relay circuits?

A. ANSI

B. Cisco

C. LMI

D. DLCI

E. BECN

F. FECN


CCNP / BSCI:

Short Answer: What is the administrative distance of ISIS?


CCNP / BCMSN:

What must be configured on a Cisco router interface before enabling CGMP?

A. PIM

B. CDP

C. OSPF

D. A distance vector protocol, preferably RIP

E. IGMP Spoofing

F. Any multicasting protocol


Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Thursday, April 13, 2006

Answers To Yesterday's CCNA And CCNP Practice Questions

Today's Questions Coming Up Later Today!

CCNA:

Convert the dotted decimal address 240.53.51.254 to a binary string. (No choices given.)

Answer: 11110000 00110101 00110011 11111110


CCNP / BSCI:

An L1/L2 ISIS router can have an adjacency with what type or types of routers in its own area?

A. L1, L1/L2, L2

B. L1 only

C. L2 only

D. L1/L2 only

E. L1, L2

Answer: A. An L1/L2 router can form an adjacency with any of the three ISIS router types in its own area.


CCNP / BCMSN

Which of the following does NOT describe a network that would be a good candidate for PIM Dense Mode?

A. Multiple recipients located on almost every subnet in the network

B. Only a few recipients overall

C. Bandwidth to spare to allow periodic flooding

D. These statements all describe networks that should run PIM Dense Mode.

Answer: B. If there are only a few recipients, PIM Sparse Mode would be a better choice.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
CCNP / BCMSN Exam Tutorial: Introduction To Multicasting

Ever since you picked up your first CCNA book, you've heard about multicasting, gotten a fair idea of what it is, and you've memorized a couple of reserved multicasting addresses. Now as you prepare to pass the BCMSN exam and become a CCNP, you've got to take that knowledge to the next level and gain a true understanding of multicasting. Those of you with an eye on the CCIE will truly have to become multicasting experts!

Having said that, we're going to briefly review the basics of multicasting first, and then future tutorials will look at the different ways in which multicasting can be configured on Cisco routers and switches.

What Is Multicasting?

A unicast is data that is sent from one host to another, while a broadcast is data sent from a host that is destined for "all" host addresses. By "all", we can mean all hosts on a subnet, or truly all hosts on a network.

There's a quite a bit of a middle ground there! A multicast is that middle ground, as a multicast is data that is sent to a logical group of hosts, called a multicast group. Hosts that are not part of the multicast group will not receive the data.

Some other basic multicasting facts:

There's no limit on how many multicast groups a single host can belong to.

The sender is usually unaware of what host devices belong to the multicast group.

Multicast traffic is unidirectional. If the members of the multicast group need to respond, that reply will generally be a unicast.

The range of IP addresses reserved for multicasting is the Class D range, 224.0.0.0 - 239.255.255.255.

That range contains a couple of other reserved address ranges.

224.0.0.0 - 224.0.0.255 is reserved for network protocols only on a local network segment. Packets in this range will not be forwarded by routers, so these packets cannot leave the segment.

Just as Class A, Class B, and Class C networks have private address ranges, so does Class D. The Class D private address range is 239.0.0.0 - 239.255.255.255. Like the other private ranges, these addresses can't be routed, so they can be reused from one network to another.

The remaining addresses fall between 224.0.1.0 and 238.255.255.255. That's the "normal" range of multicast addresses. These addresses can be routed, so they must be unique and should not be duplicated from one network to the next.

In my next BCMSN / CCNP multicasting tutorial, we'll take a look at the different ways in which Cisco routers and switches interact to forward multicast traffic.

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
RIP isn't exactly the most complex routing protocol on the CCNA exam, but that makes it easy to overlook some of the important details you must keep in mind in order to pass the exam! To help you review for the exam, here are just a few of those details!

RIP’s default behavior is to send version 1 updates, but to accept both version 1 and 2 routing updates.

R2(config)#router rip
R2(config-router)#net 172.16.0.0
R2(config-router)#^Z

R2#show ip protocols

Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 6 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is
Incoming update filter list for all interfaces is
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Key-chain
Serial0 1 1 2

By default, RIP v2 autosummarizes routing updates sent across classful network boundaries. To disable this behavior, run no auto-summary under the RIP process.

R1#conf t
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#no auto-summary

You do not specify a subnet mask or wildcard mask when configuring RIP – just the classful network, even if you’re running RIP v2.

R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#no auto-summary
R1(config-router)#network 172.10.0.0 ?



Debug ip rip displays the routing updates and metrics as the advertisements are sent and requested. To see this in action without waiting for the next regularly scheduled update, run clear ip route *.

R1#debug ip rip
RIP protocol debugging is on
R1#clear ip route *
01:16:54: RIP: sending v1 update to 255.255.255.255 via Loopback1 (1.1.1.1)
01:16:54: network 2.0.0.0, metric 201:16:54:
network 3.0.0.0, metric 201:16:54:
network 172.16.0.0, metric 101:16:54:
network 10.0.0.0, metric 201:16:54:
RIP: sending v1 update to 255.255.255.255 via Serial0 (172.16.123.1)
01:16:54: subnet 172.16.123.0, metric 1
01:16:54: network 1.0.0.0, metric 1
01:16:54: network 2.0.0.0, metric 2
01:16:54: network 3.0.0.0, metric 2
01:16:54: network 10.0.0.0, metric 2

To see only the routes discovered by a routing protocol, run show ip route followed by the name of the protocol:

R1#show ip route rip
R 2.0.0.0/8 [120/1] via 172.16.123.2, 00:00:26, Serial0
R 3.0.0.0/8 [120/1] via 172.16.13.2, 00:00:09, Serial1
[120/1] via 172.16.123.3, 00:00:09, Serial0
R 10.0.0.0/8 [120/1] via 172.16.13.2, 00:00:09, Serial1
[120/1] via 172.16.123.3, 00:00:09, Serial0
[120/1] via 172.16.123.2, 00:00:26, Serial0

And don't forget - to turn off all currently running debugs, run undebug all.

R1#undebug all
All possible debugging has been turned off

Don't overlook RIP and IGRP when it comes to the CCNA exam. OSPF and EIGRP are more complex to configure, but you need to understand how distance vector protocols work in order to pass the CCNA!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com

Wednesday, April 12, 2006

Answers To Monday's CCNA And CCNP Practice Questions

CCNA:

The "NV" in "NVRAM" stands for non-volatile. What does this term mean? Choose all that apply.

A. The contents of NVRAM cannot be changed.

B. The contents of NVRAM are not lost on reboot.

C. The contents of NVRAM cannot be copied.

D. The contents of NVRAM cannot be erased.

ANSWER: B. Non-volatile RAM is so named because the contents are not lost on a reload. The contents of NVRAM can be changed, can be copied, and can be erased.


CCNP / BSCI:

Which of the following statements does NOT describe EIGRP? Choose all that apply.

A. Uses PDMs to support IP, IPX, and AppleTalk

B. Supports VLSM

C. Allows route summarization at the interface level

D. Fast convergence

E. Static neighbor discovery

ANSWER: E. EIGRP does use PDMs to support those three protocols, it does support VLSM, it does allow route summarization at the interface level, and it does converge quickly. There is no static neighbor discovery mechanism in EIGRP.


CCNP / BCMSN

At what layer of the Cisco three-layer hierarchical model should the root bridge be found?

A. Physical

B. Core

C. Distribution

E. Data Link

F. Access

G. End User

ANSWER: B. To optimize STP operation, the root switch should be found in the core layer of Cisco's three-layer hierarchical model.


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Tuesday's CCNA And CCNP Practice Questions And Answers

CCNA:

The "NV" in "NVRAM" stands for non-volatile. What does this term mean? Choose all that apply.

A. The contents of NVRAM cannot be changed.

B. The contents of NVRAM are not lost on reboot.

C. The contents of NVRAM cannot be copied.

D. The contents of NVRAM cannot be erased.

ANSWER: B. "non-volatile" means that the contents are not lost on a reload.


CCNP / BSCI:

Which of the following statements does NOT describe EIGRP? Choose all that apply.

A. Uses PDMs to support IP, IPX, and AppleTalk

B. Supports VLSM

C. Allows route summarization at the interface level

D. Fast convergence

E. Static neighbor discovery

ANSWER: E. EIGRP does use PDMs, it does support VLSM, it does allow route summarization at the interface level, and it converges quickly. It does not have static neighbor discovery.


CCNP / BCMSN

At what layer of the Cisco three-layer hierarchical model should the root bridge be found?

A. Physical

B. Core

C. Distribution

E. Data Link

F. Access

G. End User

ANSWER: B. The root bridge will ideally be found at the core layer.


Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Cisco Announces New Wireless Certifications

Demand for wireless specialists is growing every day, and Cisco has announced two new wireless certifications to help meet this demand. Read more about them and the requirements by following this link:
www.cisco.com/web/learning/le3/whats_new/new_wireless_certifications.html

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Wednesday's CCNA / CCNP Practice Questions

Answers to Tuesday's questions will be posted tonight.

CCNA:

Convert the dotted decimal address 240.53.51.254 to a binary string. (No choices given.)


CCNP / BSCI:

An L1/L2 ISIS router can have an adjacency with what type or types of routers in its own area?

A. L1, L1/L2, L2

B. L1 only

C. L2 only

D. L1/L2 only

E. L1, L2


CCNP / BCMSN

Which of the following does NOT describe a network that would be a good candidate for PIM Dense Mode?

A. Multiple recipients located on almost every subnet in the network

B. Only a few recipients overall

C. Bandwidth to spare to allow periodic flooding

D. These statements all describe networks that should run PIM Dense Mode.
CCNP / BCMSN Exam Tutorial: The Core Layer Of The Cisco Three-Layer Hierarchical Model

In this section, you're going to be reintroduced to a networking model you first saw in your CCNA studies. No, it's not the OSI model or the TCP/IP model - it's the Cisco Three-Layer Hierarchical Model. Let's face it, just about all you had to do for the CCNA was memorize the three layers and the order they were found in that model, but the stakes are raised here in your CCNP studies. You need to know what each layer does, and what each layer should not be doing. This is vital information for your real-world network career as well, so let's get started with a review of the Cisco three-layer model, and then we'll take a look at each layer's tasks. Most of the considerations at each layer are common sense, but we'll go over them anyway!


Today we’ll take a look at the core layer of the Cisco model.

The term core switches refers to any switches found here. Switches at the core layer allow switches at the distribution layer to communicate, and this is more than a full-time job. It's vital to keep any extra workload off the core switches, and allow them to do what they need to do - switch! The core layer is the backbone of your entire network, so we're interested in high-speed data transfer and very low latency - that's it!

Core layer switches are usually the most powerful in your network, capable of higher throughput than any other switches in the network. Remember, everything we do on a Cisco router or switch has a cost in CPU or memory, so we're going to leave most frame manipulation and filtering to other layers. The exception is Cisco QoS, or Quality of Service. QoS is generally performed at the core layer. We'll go into much more detail regarding QoS in another tutorial, but for now, know that QoS is basically high-speed queuing where special consideration can be given to certain data in certain queues. (You’ll soon find that this is a very basic definition!)

We always want redundancy, but you want a lot of redundancy in your core layer. This is the nerve center of your entire network, so fault tolerance needs to be as high as you can possibly get it. Root bridges should also be located in the core layer.
The importance of keeping unnecessary workload off your core switches cannot be overstated. In the next part of this BCMSN tutorial, we’ll take a look at how the other layers of the Cisco three-part model do just that.

Tuesday, April 11, 2006

A Quick Review Of The TCP/IP Networking Model

The OSI model is the model that most networking personnel are familiar with, but to earn your CCNA, you need to know the OSI model, the TCP/IP model, and how the two map to each other.

The four layers of the TCP/IP architecture can be compared to certain levels of the OSI model. It’s important to know what each level of the TCP/IP protocol architecture does, and how these layers map to the OSI model.

The Application Layer of the TCP/IP model performs much the same tasks as the Application, Presentation, and Session layers of the OSI model.

The Transport layer in the TCP/IP architecture is similar to the Transport layer in the OSI model. This layer can use TCP or UDP as well.

The Internetwork layer in the TCP/IP architecture uses IP addresses to determine how packets should be routed. Remember that the OSI model uses IP addresses, or “Layer 3 Addresses”, at the Network layer. The two layers do much the same thing. This layer is also referred to in the TCP/IP model as the Internet layer.

The Network Interface layer in the TCP/IP architecture serves to define the protocols and the hardware needed to actually deliver the data across the network. The Network Interface model does the work of both the Data Link and Physical Layers in the OSI model.

Keeping all this straight can be very confusing when you first start your CCNA studies. Concentrate on the OSI model in your studies, but make sure you know how the TCP/IP model maps to that model and you'll be ready for CCNA exam success!

To your Cisco success,

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Monday's CCNA / CCNP Questions And Answers

CCNA:

What devices typically make up a Frame Relay cloud?

A. Frame Relay routers (DCEs)

B. Frame Relay routers (DTEs)

C. Frame Relay switches (DCEs)

D. Frame Relay switches (DTEs)

ANSWER: C. Frame Relay clouds consist of Frame Relay switches, which are DCEs (which stands for Data Communications Equipment or Data Circuit-terminating Equipment, depending on which piece of documentation you're reading!).

BSCI:

What is the highest AS number available in the BGP private AS range?

A. 64512

B. 64555

C. 65535

D. 65555

E. 32768

ANSWER: C. The range of private AS numbers is 64512 - 65535.


BCMSN:

Which of the following interface-level commands enables Loop Guard?

A. spanning-tree loop guard

B. spanning-tree guard loop

C. loop guard run

D. loop guard enable

E. run loop guard

F. enable loop guard

ANSWER: B. Use the interface-level command spanning-tree guard loop to enable Loop Guard.

SW2(config-if)#int fast 0/5
SW2(config-if)#spanning-tree guard loop

Chris Bryant
CCIE #12933
www.thebryantadvantage.com
Tuesday's CCNA / CCNP Practice Questions

Answers to Monday's questions will be posted later today!

CCNA:

The "NV" in "NVRAM" stands for non-volatile. What does this term mean? Choose all that apply.

A. The contents of NVRAM cannot be changed.

B. The contents of NVRAM are not lost on reboot.

C. The contents of NVRAM cannot be copied.

D. The contents of NVRAM cannot be erased.


CCNP / BSCI:

Which of the following statements does NOT describe EIGRP? Choose all that apply.

A. Uses PDMs to support IP, IPX, and AppleTalk

B. Supports VLSM

C. Allows route summarization at the interface level

D. Fast convergence

E. Static neighbor discovery


CCNP / BCMSN

At what layer of the Cisco three-layer hierarchical model should the root bridge be found?

A. Physical

B. Core

C. Distribution

E. Data Link

F. Access

G. End User


Chris Bryant
CCIE #12933
www.thebryantadvantage.com

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