Which two BGP mechanisms are used to prevent routing loops when using a design with redundant route reflectors? (Choose two.)

Which two BGP mechanisms are used to prevent routing loops when using a design with redundant route reflectors? (Choose two.)
A . Cluster-list
B . AS-Path
C . Originator ID 
D . Community 
E . Origin

View Answer

Answer: A,C

Explanation: 

As the iBGP learned routes are reflected, routing information may loop.

The route reflector model has the following mechanisms to avoid routing loops:

– Originator ID is an optional, nontransitive BGP attribute. It is a 4-byte attributed created by a route reflector.

The attribute carries the router ID of the originator of the route in the local autonomous system. Therefore, if amisconfiguration causes routing information to come back to the originator, the information is ignored.

– Cluster-list is an optional, nontransitive BGP attribute. It is a sequence of cluster IDs that the route haspassed. When a route reflector reflects a route from its clients to nonclient peers, and vice versa, it appendsthe local cluster ID to the cluster-list. If the cluster-list is empty, a new cluster-list is created. Using this attribute, a route reflector can identify if routing information is looped back to the same cluster due to misconfiguration. If the local cluster ID is found in the cluster-list, the advertisement is ignored.