Why should iBGP sessions be fully meshed within a Transit AS?
A.
BGP requires redundant TCP sessions between iBGP peers.
B.
A full mesh allows for optimal routing within the Transit AS.
C.
Routes learned via iBGP are never propagated to other eBGP peers.
D.
Routes learned via iBGP are never propagated to other iBGP peers.
E.
Routes learned via eBGP are never propagated to other iBGP peers.
Explanation:
Any two routers that have formed a TCP connection in order to exchange BGP routing information
are called peers or neighbors. It is important to remember that the BGP peers will never become
established unless there is IP connectivity between the two peers.
BGP does not advertise routes learned by way of IBGP peers to other IBGP peers. If BGP did,
BGP routing inside the AS would present a dangerous potential for routing loops. For IBGP routers
to learn about all BGP routes inside the AS, they must connect to every other IBGP router in a full
IBGP mesh. This full mesh needs to be only logical, not physical. In other words, as long as the
IBGP peers can connect to each other using TCP/IP, a logical full mesh can be created even if the
routers are not directly connected