Which three statements are true about BGP default operations? (Choose three.)
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A. B. C. D. E.ABE
BGP (Border Gateway Protocol) is an inter-domain routing protocol used to exchange routing information between different autonomous systems (ASes) on the internet. Here are the explanations for the given options:
A. IBGP peers advertise routes received from EBGP peers to other IBGP peers. This statement is true. When an IBGP peer receives a route from an EBGP peer, it will advertise this route to its other IBGP peers, so that all IBGP peers in the same AS will learn about the new route.
B. IBGP peers do not advertise routes received from IBGP peers to other IBGP peers. This statement is false. By default, IBGP peers do not modify the next-hop attribute of the routes learned from IBGP peers. Therefore, if an IBGP peer learns a route from another IBGP peer, it will advertise this route to its other IBGP peers, so that all IBGP peers in the same AS will learn about the new route.
C. IBGP peers do not advertise routes received from EBGP peers to other IBGP peers. This statement is false. When an IBGP peer receives a route from an EBGP peer, it will advertise this route to its other IBGP peers, so that all IBGP peers in the same AS will learn about the new route. However, if an IBGP peer learns a route from another IBGP peer, it will not advertise this route to other IBGP peers by default.
D. IBGP peers change the next hop for routes received from EBGP peers. This statement is false. By default, IBGP peers do not modify the next-hop attribute of the routes learned from EBGP peers. Therefore, if an IBGP peer learns a route from an EBGP peer, it will advertise this route to its other IBGP peers without changing the next-hop attribute.
E. EBGP peers advertise routes learned from IBGP or EBGP peers to other EBGP peers. This statement is true. By default, EBGP peers will advertise any route learned from either an IBGP or an EBGP peer to its other EBGP peers. This allows routes learned from one AS to be propagated to other ASes.
Therefore, the correct answers are A, B, and E.