Which two methods are used to reduce the mesh links required between iBGP peers in the same
AS? (Choose two.)
A.
community
B.
router reflectors
C.
local preference
D.
confederations
E.
atomic aggregate
F.
MED
Explanation:
Route Reflectors
iBGP requires that all routers be configured to establish a logical connection with all other iBGP
routers. The logical connection is a TCP link between all iBGP-speaking routers. The routers in
each TCP link become BGP peers. In large networks, the number of iBGPmeshed peers can
become very large. Network administrators can use route reflectors to reduce the number of
required mesh links between iBGP peers. Some routers are selected to become the route
reflectors to serve several other routers that act as route-reflector clients. Route reflectors allow a
router to advertise or reflect routes to clients. The route reflector and its clients form a cluster. All
client routers in the cluster peer with the route reflectors within the cluster. The route reflectors
also peer with all other route reflectors in the internetwork. A cluster can have more than one route
reflector.
Confederations
Another method to reduce the iBGP mesh within an autonomous system is BGP confederations.
With confederations, the autonomous system is divided into smaller, sub autonomous systems,
and the whole group is assigned a confederation ID. The sub-ASNs or identifiers are not
advertised to the Internet but are contained within the iBGP networks.
The routers within each private autonomous system are configured with the full iBGP mesh. Each
sub-autonomous system is configured with eBGP to communicate with other sub-autonomous
systems in the confederation. External autonomous systems see only the ASN of the
confederation, and this number is configured with the BGP confederation identifier.