Wednesday, February 06, 2008

It's Wednesday, February 6, and here are the answers to Tuesday's questions!

CCNA Certification:

The term used for an OSPF path metric is ____________ .

Extra credit: What formula does OSPF use to calculate that metric?

Answer: OSPF's metric is referred to as cost, and the calculation is 100,000,000 / interface speed in bps.


Cisco CCENT / CompTIA Network+ Question:

Which of the following do TCP and UDP headers have in common?

A. sequence number

B. source port

C. source IP address

D. window

E. destination port

F. destination IP address

G. ACK bit

H. reset bit

Answer: B, E. In addition to the source port and destination port numbers, the UDP and TCP headers also have a checksum field in common.


CCNP Certification / BSCI Exam:

In ISIS, what is the most efficient point of a network at which to perform route summarization?

A. An L1 router.

B. An L2 router.

C. An L1/L2 router.

D. A DIS router.

Answer: C. L1/L2 routers are area boundary routers in ISIS, and this is the most efficient point at which to configure route summarization


CCNP Certification / BCMSN Exam:

Short answer: An HSRP router is the primary router and it has a priority of 100. Another router comes online in the same group and it has a priority of 107. Does the new router become the primary? If so, why? If not, what additional configuration is needed to make it the primary?

Answer. By default, the new router with the higher priority will not become the primary router. To allow a router with a higher priority to take over the role of HSRP primary from an existing and normally functioning primary, the preempt option must be configured on the router with the higher priority.

Let's use a two-router HSRP deployment as an example. R2 is the standby, R3 is the primary ("active"), and both have an HSRP priority of 100. Raising R2's priority to 150 does not automatically make it the primary, as shown below.

R2(config)#interface ethernet0
R2(config-if)#standby 5 priority 150

R2#show standby
Ethernet0 - Group 5
Local state is Standby, priority 150
Hellotime 4 sec, holdtime 12 sec Next hello sent in 0.896
Virtual IP address is 172.12.23.10 configured
Active router is 172.12.23.3, priority 100 expires in 8.072
Standby router is local 1 state changes, last state change 00:14:24

R2 now has a higher priority, but R3 is still the active router. R2 will not take over as the HSRP primary until R3 goes down - OR the preempt option is configured 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 172.12.23.10 configured
Active router is local
Standby router is 172.12.23.3 expires in 10.204
Virtual mac address is 0000.0c07.ac05 2 state changes, last state change 00:00:13

New questions posted later today!

To your success,

Chris Bryant

CCIE #12933

http://www.thebryantadvantage.com/



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