VRF-Lite - Implications of using Loopback not in VRF as the Router-Id

Unanswered Question
Jul 21st, 2009

Hi, I have multiple vrf's configured on a device and than a shared vrf. The shared VRF is used to form a ipv4 iBGP session between a redundant horizontal switch and an eBGP session with a downstream switch across a firewall. All the interfaces on this switch will be SVIs and they are in a VRF. I have a Loopback 0 interface configured however I haven't made that part of a VRF and its part of the Global RT. I have a Loopback 1 which I have in the shared VRF which is used for the iBGP peering.

1. Is there any downside to using loopback 0 as the BGP Router-ID even though the other devices cannot reach Loopback 0 since its not being advertised?

2. Since Loopback0 is in the Global RT and the rest of the environment is only reachable via the Shared VRF is there any way to advertise this loopback in the shared VRF? I tried creating a VRF static route with a 'Global' keyword however am not sure what I should specify for the return traffic or what kind of route I should enter in the Global RT. Thx for your help.

I have this problem too.
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vdadlaney Wed, 07/22/2009 - 04:39

Hi Reza,

Thanks for the reply. I had read that post however I was more interested in the question which relates to using the loopback0 which is not a part of the VRF as a router-id in BGP even though its not advertised anywhere. What would be the impact of doing this. thx

amit.bhagat Wed, 07/22/2009 - 17:14

Hi,

You can use the Loopback IP address as a BGP router-id even if you dont advertise it at all.

In MPLS VPN, you can assign per-VRF BGP router-id meaning different router-IDs for each VRF under IPv4 Address-family.

http://www.cisco.com/en/US/docs/ios/12_2sr/12_2sra/feature/guide/srbgprid.html

However, I am not sure what advantage you will get by using different a IP address to form peer and a different router-id.

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