Which two statements about BGP are accurate? (Choose two.)
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A. B. C. D.BD
BGP (Border Gateway Protocol) is a routing protocol used to exchange routing information among different autonomous systems (AS) on the Internet. Here are the accurate statements about BGP:
B. BGP uses TCP port 179 for connectivity. BGP uses TCP (Transmission Control Protocol) as its transport protocol for communication. The default TCP port for BGP is 179, which is used to establish a TCP connection between BGP routers. The use of TCP provides reliable and ordered delivery of BGP messages between routers.
D. Internal peering sessions require an underlying IGP. When BGP is used within an autonomous system (AS), it is referred to as Internal BGP (iBGP). Internal peering sessions require an underlying Interior Gateway Protocol (IGP) to provide reachability information for BGP routers within the same AS. The IGP is used to advertise network prefixes within the AS, and iBGP is used to propagate BGP routing information among the BGP routers in the same AS.
A. BGP uses UDP port 500 for connectivity. This statement is incorrect. BGP does not use UDP (User Datagram Protocol) for connectivity. It uses TCP as its transport protocol, as mentioned earlier.
C. External peering sessions require an underlying IGP. When BGP is used to exchange routing information between different AS, it is referred to as External BGP (eBGP). External peering sessions do not require an underlying IGP because the BGP routers in different AS are not expected to have a direct link. Instead, eBGP sessions are established between the border routers of different AS, and BGP is used to exchange reachability information for the prefixes that belong to each AS.
In conclusion, the accurate statements about BGP are that it uses TCP port 179 for connectivity, and internal peering sessions require an underlying IGP.