How to find out the network address for the BGP protocol?

Question

Border Gateway Protocol

I need to write a c++ program that would build a routing table for the BGP protocol from a pcap packet.
Tell me how to determine the network address and mask of the destination host in wireshark?
BGP has an NP_REACH_NLRI attribute in Path Attributes, which, according to the Internet, notifies about a possible path to a partner, it has its own NEXT_HOP and NLRI Prefix (network address, which, however, looks doubtful).


However, in the RFC, the source of the network address specifies the NLRI Prefix, which is NOT included in the Path Attributes


. In this case, the protocol uses either option 1 or 2, but not both together.
Why in some protocols NLRI Prefix can only be found in Path Attributes, and can this representation be used to determine the network address and next hop?

Answer 1

Tell me how to determine the network address and mask of the destination host in wireshark?

See the RFC to understand how NLRI fields and NEXT_HOP attributes are related in an UPDATE message.