MPLS VPN PE and RR behavior difference w.r.t. treating VPNv4 prefixes?

[mukupatil]

VRRs accept and store all BGP VPNv4 routes but PE accepts only routes belong to its VRF (by matching RT). Howcome RR behavior differ from PE ?

Thanks in advance.

[Luc De Ghein · Accepted solution]

Hi,

Well, if the RRs would not store all the routes, then it could lead to some PE routers missing some prefixes that they are interersted in. If the RRs would not store all the routes, then you'd need to revert back to a full mesh between all PE routers. The function of the RRs is to serve all the PE routers for all the VRFs, hence they need to store and propagate all the vpnv4 routes.

Thanks,

Luc

[Peter Paluch]

Hello Luc,

We can say that effectively, running BGP RR implies no bgp default route-target filter - correct?

Best regards,

Peter

[Luc De Ghein · Accepted solution]

Yes. Correct.

Thanks,

Luc

[mukupatil]

Hello Luc,

Thanks for clarity.

I really appreciate you for writing a wonderful book on MPLS

I have one small question on the example which you have mentioned in your book under “Example of an MPLS VPN Network with RR Groups”.

Q.1 The example given does it just to explain the “bgp rr-group” concept or is having any practical use?

Q.2 If any one of the RR shown in the diagram, if goes down then VPN sites advertise via that RR will not be able to communicate?

Apologies If I have overlooked anything.

[Luc De Ghein · Accepted solution]

Hi,

I have one small question on the example which you have mentioned in your book under Example of an MPLS VPN Network with RR Groups.

Q.1 The example given does it just to explain the bgp rr-group concept or is having any practical use?

> It explains the rr-group concept. The usage is to divide the set of vpnv4 routes stored on RRs

Q.2 If any one of the RR shown in the diagram, if goes down then VPN sites advertise via that RR will not be able to communicate?

> Yes. So, to keep redundancy, you'll need to add another set of RRs. You effectively double the nr of RRs needed with rr-groups.

Thanks,

Luc