Swap labels vrf ASBR

[Ignacho]

Hi, in BGP option B the ASBR swap label by route o by vrf if the ASBR have the vrf configure? 

[Harold Ritter]

Hi @Ignacho ,

The ASBR allocates one label per prefix per egress PE by default, even if the egress PEs are configured for per-vrf label allocation mode. This means that the switching will be performed using a different label for each and every prefix.

You can change the label allocation mode on the ASBR using the following command:

router bgp xxx

address-family vpnv4 unicast
label mode per-nexthop-received-label

This basically means that the ASBR allocates one label per vrf per egress PE, assuming that the egress PE is configured for per-vrf label allocation mode.

Regards,

[Ignacho]

Thanks Harold for your answer, i was test this command before but doesn't works when the ASBR have configure the same vrf that's the PE has, do you have another suggestion about that? 

[Harold Ritter]

Hi @Ignacho ,

You would normally use this command to improve the ASBR scaling.

If scaling is the issue you are trying to solve, my recommendation would be to move the VRFs away from the ASBR and use it strictly as an ASBR, rather than an ASBR/PE.

Regards, 

[Ignacho]

Hi @Harold Ritter ,

In our escenary, the other ASBR is a Juniper router and it can swap label by vrf inclusive when it is ASBR/PE because it has the vrf configured.

Well, the behavier of ASBR cisco is normally like that or ir can do anything, maybe with a policy or similar?

Regards,

Ignacho

[Harold Ritter]

Hi @Ignacho ,

I suspect that the behavior you are seeing on the ASBR is due to the XR version you are running.

What IOS-XR version do you run on the ASBR and what device is it?

I just ran a quick test with 7.4.1 and the ASBR only allocates one label per vrf per egress PE even if the ASBR is also configured as a PE for the given VRF.

Regards,

[Ignacho]

Hi @Harold Ritter , is a ASR 9006 and have 6.7.3 versión ios-xr. In our case, i see this labels on ASBR:

1.- vrf not configure

show bgp vpnv4 unicast rd 6147:10014 l$
Sun Mar 24 23:52:43.708 
*>i192.168.104.9/32 10.11.0.207 102 24135
*>i192.168.114.9/32 10.11.0.207 102 24135

2.- vrf configured 

show bgp vpnv4 unicast rd 6147:10000 l$

Sun Mar 24 23:52:54.714

*>i10.10.0.28/30 10.11.0.207 99 24226

*>i10.119.94.0/24 10.11.0.207 99 24227

*>i172.16.100.1/32 10.11.0.207 99 24231

*>i172.16.100.2/32 10.11.0.207 99 24232

Regards,

Renzo

[Harold Ritter]

Hi @Ignacho ,

I found the following bug that could be related. Do you use a unique RD on the ASBR or do you share the same RD with the PEs?

https://bst.cisco.com/bugsearch/bug/CSCwa55054

I tried using the same RD on the ASBR and the PE in my lab and see the same behavior you are seeing. The issue goes away when you use a different RD on the ASBR.

Regards,

[Ignacho]

Hi @Harold Ritter , i use the same RD. Yes, i change the rd in the ASBR and works ok the swap labels. Well, this bug don´t have solution for the moment?, thanks for your help.

Regards,

Renzo

[Harold Ritter · Accepted solution]

Hi @Ignacho ,

This bug does not have a fix yet. I imagine it is because an easy workaround is available.

Regards,