BGP Attributes for EBGP Peers

CDE

BGP (Border Gateway Protocol) is an internet routing protocol used to exchange routing information between different Autonomous Systems (AS). BGP is critical for the proper functioning of the internet, as it enables different networks to communicate with each other and exchange traffic.

When BGP speakers exchange routing information, they exchange BGP attributes, which are pieces of information that describe the characteristics of the routes being advertised. Some of these attributes are mandatory, meaning that they must be sent to EBGP (External BGP) peers, while others are optional.

The three BGP attributes that must be sent to EBGP peers are:

1. Origin: This attribute identifies the origin of the route being advertised. The origin can be one of three types: IGP (Interior Gateway Protocol), EGP (Exterior Gateway Protocol), or Incomplete. The IGP origin indicates that the route was learned from an internal routing protocol such as OSPF or IS-IS. The EGP origin indicates that the route was learned from an external routing protocol such as EIGRP or RIP. The Incomplete origin indicates that the origin of the route is unknown.

2. AS Path: This attribute lists the AS numbers that the route has traversed to reach the advertising BGP speaker. The AS Path is used to prevent routing loops and to provide path information to help select the best path to a destination.

3. Next Hop: This attribute identifies the next-hop IP address that should be used to reach the destination network. The Next Hop attribute is essential for forwarding traffic correctly to the destination network.

The other BGP attributes mentioned in the question are optional attributes that may or may not be sent to EBGP peers. The local preference attribute is used to indicate the preference for a particular route within the local AS. The atomic aggregator attribute is used to indicate that the BGP speaker has aggregated several routes into a single route.