Correct Answer: E
Explanation/Reference:
Explanation:
The Border Gateway Protocol (BGP) conditional advertisement feature provides additional control of route advertisement, depending on the existence of other prefixes in the BGP table. Normally, routes are propagated regardless of the existence of a different path. The BGP conditional advertisement feature uses the non-exist-map and the advertise-map keywords of the neighbor advertise-map command in order to track routes by the route prefix. If a route prefix is not present in output of the non-exist-map command, then the route specified by the advertise- map command is announced. This feature is useful for multihomed networks, in which some prefixes are advertised to one of the providers only if information from the other provider is not present (this indicates a failure in the peering session or partial reachability).
Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/16137- cond- adv.html