peer group

[kthned]

Hi

I have a question related to peer group, As the basic advantage of "peer group" is used to reduce the amount of system resources (CPU and Memory) in an update. and it also simplifies the router cofiguration.

with the above concept, here is the configuration

router BGP 10

neighbour 10.1.1.1 remote-as 20

neighbour 10.1.2.1 remote-as 30

neighbour 10.1.3.1 remote-as 40

neighbour 10.1.4.1 remote-as 10

neighbour 10.1.4.1 route-reflector-client

neighbour 10.1.4.2 remote-as 10

neighbour 10.1.4.2 route-reflector-client

with the above configuration, it is clear to use one peer group for route-reflector clients, But is it better to use peer group for the external peers with the context of above configuration.

--

Regards

Syed Umair Ali

[mheusinger]

Hello Syed Umair Ali,

the answer is "yes" ... and "not necessarily". :-)

About the "yes": Every member of a peer-group will get the exact same BGP updates calculated for the "peer-group leader". So if you have a set of BGP peers with the same outgoing updates, a peer-group makes sense.

It keeps your router from going through the BGP table for every neighbor to prepare the updates. This will only happen once for the leader and the resulting updates will be sent to all peer-group members. Hence the CPU load is lowered.

As to "not necessarily": starting with IOS 12.3(4)T Cisco BGP routers will use "BGP Dynamic Update Peer-Groups".

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801d3b32.html

Basically the router automatically groups peers with respect to outgoing updates, just like if you configured peer-groups in an earlier version of IOS. So if your IOS is newer you could omit peer-group configuration from a performance point of view.

My personal taste is to use peer-groups whenever possible. Your config would then look like this:

router BGP 10

neighbour eBGP-Peer peer-group

neighbour RR-client peer-group

neighbour RR-client route-reflector-client

neighbour RR-client remote-as 10

neighbour 10.1.1.1 peer-group eBGP-Peer

neighbour 10.1.1.1 remote-as 20

neighbour 10.1.2.1 peer-group eBGP-Peer

neighbour 10.1.2.1 remote-as 30

neighbour 10.1.3.1 peer-group eBGP-Peer

neighbour 10.1.3.1 remote-as 40

neighbour 10.1.4.1 peer-group RR-client

neighbour 10.1.4.2 peer-group RR-client

Hope this helps! Please use the rating system.

Regards, Martin

[kthned]

Thanks Martin,

But By defining "eBGP-Peer" peer group in your configuration, is this configuration saving any resources(CPU/Memory ) of router. ???

[mheusinger]

Well,

it depends on your IOS version. Before 12.3T, i.e. without dynamic peer-groups, this lowers CPU load, after the invention of dynamic peer-groups there should be not much difference.

Regards, Martin