Tuesday, July 29, 2008

Here are the answers to the Cisco certification exam practice questions posted on Monday, July 28.

Be sure to read today's other blog posts for links to new practice exam question sets posted on the main website!

CCNA Certification:

What single command would double every RIP value show in the following command output?

R1#show ip protocols
Routing Protocol is "rip"
Sending updates every 30 seconds
Invalid after 180 seconds, hold down 180, flushed after 240

Answer: Use the timers basic command to change RIP values. IOS Help shows how to use this command to double each value:

R1(config)#router rip

R1(config-router)#timers basic
R1(config-router)#timers basic ?

<0-4294967295> Interval between updates
R1(config-router)#timers basic 60 ?

<1-4294967295> Invalid
R1(config-router)#timers basic 60 360 ?

<0-4294967295> Holddown
R1(config-router)#timers basic 60 360 360 ?

<1-4294967295> Flush
R1(config-router)#timers basic 60 360 360 480

CCENT Certification:

You're configuring a Cisco switch and attempt to place a port into a VLAN that has not yet been created. What will happen, and what message should you expect to see?

Answer: The switch will dynamically create the VLAN and send you a message indicating just that. Here's the message I received when placing a port into VLAN 500, a VLAN that did not previously exist on this switch:

SW1(config)#int fast 0/1

SW1(config-if)#switchport mode access

SW1(config-if)#switchport access vlan 500

% Access VLAN does not exist. Creating vlan 500

CCNA Security Certification / CCNP ISCW Exam:

You're working in SDM to configure an Easy VPN Server. You'll have three options for authenticating your Easy VPN Clients. What are they?

Answer: The choices are Pre-shared key, Digital Certificates, and Both, as shown here in this screen shot from my CCNA Security Study Package. (Click the image for a larger view.)

CCNP Certification / BSCI Exam:

What do the following IPv4 fields have in common as they relate to IPv6?

Header Length
Fragment Offset
Header Checksum

Answer: None of them made the cut to IPv6 - they're IPv4-only fields.

CCNP Certification / BCMSN Exam:

What single word allows an HSRP router to take over as the Active router even if the current Active route is online?

Answer: preempt. In the following example, R2 was not the Active router even though its priority was higher than the current Active router. After reconfiguring R2's priority statement with the preempt option, R2 becomes the Active router.

Note that may preempt now appears in the output of show standby on R2.

R2(config-if)#standby 5 priority 150 preempt

1d11h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Standby -> Active

R2#show standby
Ethernet0 - Group 5
Local state is Active, priority 150, may preempt
Hellotime 4 sec, holdtime 12 sec
Next hello sent in 1.844
Virtual IP address is configured
Active router is local
Standby router is expires in 10.204
Virtual mac address is 0000.0c07.ac05
2 state changes, last state change 00:00:13

CCNP / ONT Exam:

What headers are compressed by RTP Header Compression?

RTP HC will compress RTP headers, certainly - but it will also compress IP and UDP headers.

RTP compression can result in quite a bit of overhead reduction. Consider those three headers and their size:

IP Header: 20 bytes

UDP Header: 8 bytes

RTP Header: 12 bytes

RTP HC will result in that overall header size being reduced to anywhere from 2 to 4 bytes, depending on whose documentation you're reading.

I'll post new questions for you later today!

To your success,

Chris Bryant
CCIE #12933

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