Which two conditions can cause BGP neighbor establishment to fail? (Choose two.)

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

B.
The IBGP neighbor is not directly connected.

C.
BGP synchronization is enabled in a transit autonomous system with fully-meshed IBGP
neighbors.

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

E.
The BGP neighbor is referencing an incorrect autonomous system number in its
neighbor statement.

Explanation:
An underlying connection between two BGP speakers must be established before any
routing information is exchanged. This connection takes place on TCP port 179 so if an
access list blocks all TCP traffic between the two BGP neighbors, BGP neighbor
relationship can not be established -> A is correct.
The IBGP neighbors don’t need to be directly connected -> B is not correct.
BGP synchronization only prevents routes sent to other EBGP neighbors before that route
exists in the routing table. It doesn’t prevent BGPneighbor relationship -> C is not correct.
After the first initial exchange (which exchanges routes and synchronize their tables), a BGP
speaker will only send further updates upon a change in the network topology -> BGP does
not have a fixed update interval -> D is not correct.
BGP neighbor relationship is established when both ends (routers) are manually configured
with the “neighbor neighbor-IP remote-as neighbor-AS” command on both sides of the
connection. If the neighbor-AS is wrong, the neighbor relationship can not be established ->
E is correct.