Use of Confederation

[abdul.qadir5001]

When we have Route Reflector then why we use confederation. Please need expert opinion on it. Thanks

[Giuseppe Larosa]

Hello @abdul.qadir5001 ,

it is a design choice the two features can be used together or not.

By using only route reflectors higher scalability can be achieved using two levels of BGP reflections first level BGP RRS are clients of top level RRS that need a full iBGP mesh .

I have seen this solution used for address family ipv4 unicast.

On the other hand instead of using two levels of BGP reflections an ISP could choice to deploy BGP confederations and to use BGP RRS inside each mini AS.

To be noted the greatest difference is that in the second case we don't need  an IGP routing domain that spans all the ISP network each BGP confederation can have its own IGP.

Hope to help

Giuseppe

[abdul.qadir5001]

Ok we can say that Route Reflector and Confederation are two different methods to solve the same issue (IBGP full mesh)?

But if we compare both methods then confederation looks difficult. 

1) We need to perform configuration on each device and each device must support confederation

2) Logical topology of the network need to be modified

3) sub AS in confederation need to establish eBGP peering

4) Confederation cannot be used in large network and it has only few application

Please share your expert opinion on it. Thanks

[Giuseppe Larosa · Accepted solution]

Hello @abdul.qadir5001 ,

I agree on points 1) - 3) Route Reflectors are much easier to deploy.

4) no it is the opposite the BGP confederations are used by very big service providers for the reason that this way they can split the IGP routing domains of course inside each BGP confed mini AS RRS are deployed.

Hope to help

Giuseppe