BGP: Border Gateway Protocol – As defined in RFC 1771, BGP is an interdomain routing protocol. You would use BGP to exchange routing information between autonomous systems. It’s usually configured between two directly connected routers that belong to different autonomous systems and the routers must first become established neighbors. TCP Port 179 is reserved for the BGP protocol to establish connections with neighbors. For more information on BGP, see the article on Border Gateway Protocol documentation.
MBGP: Multiprotocol Border Gateway Protocol – Bigger and better BGP. MBGP is an enhanced form of BGP which has IP routing information about other protocols. It also carries information about reachable and non-reachable destinations in the network layer (that’s Layer 3). For more, information, please see the MBGP article.
EIGRP: Enhanced IGRP – Just like MBGP is an enhanced form of BGP, EIGRP provides more compatibility than IGRP. EIGRP allows IGRP routes to be imported into EGRP, and vice versa, so it is possible to gradually add it into your existing IGRP network. For more information, see the EIGRP article.
RIP: Routing Information Protocol – A distance-vector protocol that uses hop count as its’ metric. This metric can be hops, bandwidth, delay, or multiple metrics. Distance vector protocol periodically sends the neighboring routers its entire routing table to ensure network availability. RIP is used for routing traffic and is an interior gateway protocol (IGP), which means that it performs routing within a single autonomous system. Just like IGRP, this is an old routing algorithm and could result in split horizon. For more, information, please see the RIP article.