Configuring a BGP Router ID
The router ID should be configured first when you configure BGP. The router ID is a string similar to the IP address, and is the identifier of a BGP router in an AS. You should not change the router ID after completing the configuration. By default, the BGP router ID is not configured.
Configuring BGP Local-AS
The local ASN (Autonomous System Number) should be configured when you configure BGP. An Autonomous System (AS) is a group of IP networks that are controlled by one entity, typically an Internet service provider (ISP), and that have the same routing policy. Each AS is assigned a unique AS number, which identifies an AS on a BGP network.
The AS_Path attribute records all the AS numbers that a route passes through, from the source to the destination, following the order of vectors.
Configuring External BGP Peering
If the AS number of the specified peer is different from the local AS number during the configuration of BGP peers, an EBGP peer is configured. To establish point-to-point connections between peer autonomous systems, 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.
Configuring Internal BGP Peering
If the AS number of the specified peer is the same as the local AS number during the configuration of BGP peers, an IBGP peer is configured.
Configuring a BGP Peer Group
A large BGP network has a large number of peers. It is difficult to configure and maintain these peers. You can add the BGP peers with the same configurations to a BGP peer group and then configure the BGP peers in batches. This simplifies peer management and improves route advertisement efficiency.
- If a BGP configuration exists on a peer and its peer group, the BGP configuration on the peer takes precedence over the configuration on the peer group.
- If the peer you want to add to a group already exists in the BGP configuration, delete it first, than add it to the peer group.
The following example commands create a peer group called Leaf1 that includes two external peers.