Cisco CCNP BSCI Practice Exam: 10 Questions On BGP

The CCNP BSCI exam is a tough one, and there’s no harder topic on that exam than BGP.   Use these practice exam questions to sharpen your basic BGP skills!

1. We'll start with a very important BGP value - which port number does BGP use to establish adjacencies?

2. Identify the true statements.

A. BGP uses the same logical grouping concept as EIGRP.

B. BGP uses the same logical grouping concept as OSPF.

C. BGP neighbors must be directly connected.

D. BGP neighbors need not be directly connected.

3. What required value is missing from the following BGP command?

R1(config-router)#neighbor 172.12.123.3

% Incomplete command.

4. Identify the well-known mandatory BGP attributes.

A. AS_PATH

B. Local Pref

C. Atomic Aggregate

D. Origin

E. Next-Hop

5. Identify the well-known discretionary BGP attributes.

A. AS_PATH

B. origin

C. aggregate

D. Local Pref

E. next-hop

F. atomic aggregate

6. Give the three possible values for a BGP origin code and describe the meaning of each.

7. Of the BGP values discussed in the previous question, list them in order from most-preferred to least-preferred.

8. In the BGP best path selection process, what attribute is used first on a non-Cisco router?

9. Identify the true statements regarding the BGP attribute weight.

A. On Cisco routers, it's the first attribute considered in the best-path selection process.

B. It is a Cisco-proprietary value

C. It is locally significant only

D. It is advertised to other routers as part of the BGP update process

10. In BGP terminology, what is a "soft reset"? Why would we perform such a reset, and how is it done?

Here are the answers!

1. BGP uses TCP port 179 to create and maintain adjacencies.

2. (A, D). BGP and EIGRP use autonomous systems to group routers logically. There is no requirement for BGP routers to be directly connected in order to become neighbors.

3. You must specify the potential neighbor's AS with the remote-as portion of the command.

R1(config-router)#neighbor 172.12.123.3

% Incomplete command.

R1(config-router)#neighbor 172.12.123.3 remote-as 200

4. (A, D, E). The well-known mandatory BGP attributes are AS_PATH, origin, and next-hop.

5. (D, F). The well-known discretionary BGP attributes are local preference (LOCAL_PREF) and atomic aggregate.

6. There are three possibilities for the Origin code. The letter "i" indicates the path originated from an IGP and was originated with the network command.  An “e” indicates that the route originated from an Exterior Gateway Protocol (EGP).  

Finally, an origin code of “?” means the origin is not quite clear; generally, this means the route was learned via redistribution.

7. The order of preference, most-preferred to least-preferred:  IGP, EGP, Incomplete.

8. The BGP attribute weight is used first on Cisco routers, but this is a Cisco-proprietary attribute. The first attribute considered on non-Cisco routers is local preference - the highest LOCAL_PREF is preferred.

9. (A, B, C). Weight is the first value considered in BGP path selection among multiple paths - and when the routers are Cisco routers!

There are three major points to remember about the weight attribute - it's Cisco-proprietary, it's locally significant only, and it's never advertised to other routers.

10. BGP sometimes requires the sessions to be reset in order for configured changes to take effect. Problem is, that can require tearing down the existing BGP connections - unless you use a soft reset, which resets the sessions without tearing the adjacencies down.

To perform a BGP soft reset:

R1#clear ip bgp * soft

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