Question 1.
What is the default behavior of a BGP session when policies relating to it are changed inside the local router?

a) New updates to the peer router have policies applied to them.
b) The entire BGP database to that peer is cleared and must be rebuilt.
c) All sessions on the router are reset.
d) The changes will take effect immediately.

Answer

Question 2.
What BGP attribute prevents loops inside a single route reflector cluster?

a) Confederation ID
b) Originating router ID
c) Cluster ID
d) Community

Answer

Question 3.
In the figure, which routers must have confederation peers defined?

a) Basil, Cilantro and Serrano
b) Basil and Cilantro
c) all routers
d) all routers except Serrano

Answer

Answers

Question 1.
What is the default behavior of a BGP session when policies relating to it are changed inside the local router?

a) New updates to the peer router have policies applied to them.
b) The entire BGP database to that peer is cleared and must be rebuilt.
c) All sessions on the router are reset.
d) The changes will take effect immediately.

Answer
b) The entire BGP database to that peer is cleared and must be rebuilt.

Explanation
Remember that routing policies are actually internal to the router, and are not part of the update. Import policies apply to updates received in the Adj-RIB-In, and only those that are acceptable under the policy filters go into the main RIB. In like manner, RIB information goes through advertising policies before it is placed in the Adj-RIB-Out to be advertised to neighbors.

It's not unreasonable, therefore, to assume that when a policy changes, policy filters need to be reapplied to determine the acceptable policies. Traditionally, when a policy changed, the interface(s) were reset to force reexamination of the relevant peer RIB. A hard reset of an interface, however, can result in the need to transfer and filter an entire Internet routing table, which can take several minutes and impose significant CPU demand.

Soft refresh mechanisms are available in recent IOS releases.
[3544]

Question 2.
What BGP attribute prevents loops inside a single route reflector cluster?

a) Confederation ID
b) Originating router ID
c) Cluster ID
d) Community

Answer
b) Originating router ID

Explanation
Just as a general eBGP speaker rejects incoming updates that contain the local AS number, a route reflector will reject an update that contains its own router ID.
[3545]

Question 3.
In the figure, which routers must have confederation peers defined?

a) Basil, Cilantro and Serrano
b) Basil and Cilantro
c) all routers
d) all routers except Serrano

Answer
a) Basil, Cilantro and Serrano

Explanation
Routers that need confederation peer statements are those which have confederation eBGP peering. The only routers that have confederation eBGP are Basil, Cilantro, and Serrano.
[3546]