Which three conditions can cause BGP neighbor establishment to fail? (Select three)

A.
There is an access list blocking all TCP traffic between the two BGP neighbors.

B.
The EBGP neighbor is not directly connected, and the ebgp-multi-hop option is set to the
default valu

C.
The IBGP neighbor is not directly connected.

D.
BGP synchronization is enabled in a Transit AS with fully-meshed IBGP neighbors.

E.
The BGP update interval is different between the two BGP neighbors.

F.
The BGP neighbor is referencing an incorrect AS number in its neighbor statement.

Explanation:
BGP uses TCP port 179 to establish and maintain neighbor relationships, so any access lists
or firewalls must permit this port for BGP to function.
By default, EBGP multi-hop is not enabled, so the EBGP peer must be directly connected in
order for the local BGP router to know how to reach the EBGP peer.

BGP uses neighbor statements that specify the AS number of the BGP peer. If it is the
same number as the local BGP router process, then the BGP router knows that IBGP is
used. If the AS number for the specified peer is different, then EBGP is used. Either way,
the specified neighbor must be configured correctly, or the BGP peers will not become
neighbors.