Supported Platforms
Related Documentation
- ACX, J, M, MX, QFX, SRX, T Series
- Understanding BGP
- Example: Configuring External BGP Point-to-Point Peer Sessions
- Example: Configuring Internal BGP Peer Sessions
Understanding External BGP Peering Sessions
To establish point-to-point connections between peer autonomous systems (ASs), you configure a BGP session on each interface of a point-to-point link. Generally, such sessions are made at network exit points with neighboring hosts outside the AS. Figure 1 shows an example of a BGP peering session.
Figure 1: BGP Peering Session
In Figure 1, Router A is a gateway router for AS 3, and Router B is a gateway router for AS 10. For traffic internal to either AS, an interior gateway protocol (IGP) is used (OSPF, for instance). To route traffic between peer ASs, a BGP session is used.
You arrange BGP routing devices into groups of peers. Different peer groups can have different group types, AS numbers, and route reflector cluster identifiers.
To define a BGP group that recognizes only the specified BGP systems as peers, statically configure all the system’s peers by including one or more neighbor statements. The peer neighbor’s address can be either an IPv6 or IPv4 address.
As the number of external BGP (EBGP) groups increases, the ability to support a large number of BGP sessions might become a scaling issue. The preferred way to configure a large number of BGP neighbors is to configure a few groups consisting of multiple neighbors per group. Supporting fewer EBGP groups generally scales better than supporting a large number of EBGP groups. This becomes more evident in the case of hundreds of EBGP groups when compared with a few EBGP groups with multiple peers in each group.
After the BGP peers are established, BGP routes are not automatically advertised by the BGP peers. At each BGP-enabled device, policy configuration is required to export the local, static, or IGP-learned routes into the BGP RIB and then advertise them as BGP routes to the other peers. BGP's advertisement policy, by default, does not advertise any non-BGP routes (such as local routes) to peers.
Related Documentation
- ACX, J, M, MX, QFX, SRX, T Series
- Understanding BGP
- Example: Configuring External BGP Point-to-Point Peer Sessions
- Example: Configuring Internal BGP Peer Sessions
Published: 2013-02-08
Supported Platforms
Related Documentation
- ACX, J, M, MX, QFX, SRX, T Series
- Understanding BGP
- Example: Configuring External BGP Point-to-Point Peer Sessions
- Example: Configuring Internal BGP Peer Sessions
