BGP Peer-Groups:
Why do we need bgp peer groups?
In a network, we may have a couple of eBgp neighbors and dozens of iBGP neighbors
With each Bgp neighbor, there is a lot of other policies such as filter-list/ route-map/ distribute-list. If each neighbor had different policy, no other way than applying to them individually, but, Many neighbors might require the same BGP policies like:
Configuring per-neighbor policies are burdensome:
- Takes more time to configure
- Utilizes more CPU for sending/receiving updates
Example:
- If we had lots of neighbors, it will take a lot of time…:(
- But, what if we could create a group and put all of the neighbors under that group and then configure policies for that group
(WARNING: This not actual command, just an analogy)
What is a Peer Group?
- Groups of peers to which the same outbound policies apply
- Only inbound policies can be overridden on a per-neighbor basis
- All configuration options or individual neighbors can be applied to peer groups
- Updates are generated once per group
Configuration:
- To create the peer-group:
(config-router)#neighbor
- To add neighbors to that peer-group:
(config-router)#neighbor
Example of peer-group for iBGP neighbors:
- Here, were are creating a peer-group named ‘my-company’
- And for peer-group ‘my-company’, we are saying it is in remote-as 300 and has route-map ‘Attribute’ outbound and filter-list ‘2’ outbound
- In the end, we just mention neighbor IP and mention peer-group
- Now, coming to the last command: in a peer-group, all the neighbors must have the same outbound policy. But, if we wish, we could give unique inbound policies
Example of peer-group for eBGP neighbors:
- Since, all external neighbors will be in different AS, we can’t apply ‘remote-as’ under peer-group, but, still, we can give the policies for the external neighbors under a peer-group
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