Creating bgp router-ids for IPv4 and IPv6 instances under VRF(IOS-XR)

[okochat18]

I would like to create routing in bgp as follows. How do I achieve this in IOS-XR.ASR9000. How do I do this?

----

router bgp 65000

vrf test

  address-family ipv4 unicast

  bgp router-id 1.1.1.1

  neighbor 10.10.10.10

  remote-as 4

  address-family  ipv6 unicast

  bgp router id 2.2.2.2

  neighbor 2001:f:e::1

  remote-as 4

vrf test2

  address-family ipv4 unicast

  bgp router-id 1.1.1.4

  address-family  ipv6 unicast

  bgp router id 2.2.2.4

[Harold Ritter · Accepted solution]

Hi @okochat18 ,

I am not sure on what operating system these configurations are from, but in general you can only have one BGP router id per VRF, so one for both IPv4 and IPv6. Under XR it would look something like this:

route policy accept-all

pass

end-policy

router bgp xxx

address-family vpnv4 unicast

address-family vpnv6 unicast

vrf test

rd xxx:yyy

bgp router-id 1.1.1.1

address-family ipv4 unicast

address-family ipv6 unicast

neighbor 10.10.10.10

remote-as 4

address-family ipv4 unicast

route-policy accept-all in

route-policy accept-all out

neighbor 2001:f:e::1

remote-as 4

address-family ipv6 unicast

route-policy accept-all in

route-policy accept-all out

vrf test2

rd xxx:zzz

bgp router-id 1.1.1.4

address-family ipv4 unicast

address-family ipv6 unicast

Note that the route-policy is required in XR, as eBGP does not advertise nor receive any update by default.

Regards,

[MHM Cisco World]

@Harold Ritter is totally correct'

One router-id per vrf not per ip address family.

Maybe you asking about making ipv6 prefix using next-hop ipv4?

MHM

[okochat18]

Thanks Harold Ritter and MHM

I saw this config sample on cisco's example page sometime back
and thought it could be done per vrf per ipv4/Ipv6
====
https://www.cisco.com/c/en/us/td/docs/ios/12_2sr/12_2sra/feature/guide/srbgprid.html

Router(config-router)# address-family ipv4 vrf vrf_trans
Router(config-router-af)# neighbor 192.168.1.1 remote-as 40000
Router(config-router-af)# bgp router-id 10.99.1.1

===

Is it that IOSXR cant do it?
Was it existing and removed?

In terms of routing,
Using one Router-ID for both address-family IPv4 and address-family IPv6
wouldnt the router have problem with forming adjacency during bgp message exchanges if
the bgp router-id is the same?

To Harold: Btw the configs we completely made up to help you understand what I want to implement

[Harold Ritter]

Hi @okochat18 ,

Having a separate bgp router-id for ipv4 and ipv6 within the same VRF is not possible in IOS either.

PE1(config-router)#address-family ipv4 vrf test

PE1(config-router-af)#bgp router-id 1.1.1.1

PE1(config-router-af)#address-family ipv6 vrf test

PE1(config-router-af)#bgp router-id 1.1.1.2       

PE1(config-router-af)#do sh runn | s r b

router bgp 109

 bgp log-neighbor-changes

 !

 address-family ipv4 vrf test

  bgp router-id 1.1.1.2

 exit-address-family

 !

 address-family ipv6 vrf test

  bgp router-id 1.1.1.2

 exit-address-family

The bgp router-id will be the same for both, as can be seen above.

> wouldnt the router have problem with forming adjacency during bgp message exchanges if
the bgp router-id is the same?

You can have as many sessions as you want between two routers and all the sessions could have the same bgp router-id. The issue would be if the local bgp router-id was equal to the remote bgp router-id.

Regards,

[okochat18]

Harold, I appreciate your feedback. So glad

Currently I'm checking on my end. Will respond soon!

[okochat18]

Hi @Harold Ritter , @MHM Cisco World 

Thanks guys for your inputs last weekend.

In a scenario as shown below where the bgp router-id is actually placed in the BGP global settings.
Would the vrf pick up the ipv4 id and also the ipv6 id as separate entities?

As per my knownledge couldnt make sense of it 
============

route policy accept-all

pass

end-policy

router bgp xxx

address-family ipnv4 unicast

bgp router-id 1.1.1.1

address-family ipnv6 unicast

bgp router-id 1.1.1.2

address-family vpnv4 unicast

address-family vpnv6 unicast




vrf test

rd xxx:yyy

address-family ipv4 unicast

neighbor 10.10.10.10

remote-as 4

address-family ipv4 unicast

route-policy accept-all in

route-policy accept-all out




neighbor 2001:f:e::1

remote-as 4

address-family ipv6 unicast

route-policy accept-all in

route-policy accept-all out

[MHM Cisco World]

let me check again 
Thanks 
MHM

[Harold Ritter]

Hi @okochat18 ,

XR will not accept a different BGP router-id for v4 and v6, whether that is in the global or VRF context.

Why would it matter if the IPv4 and IPv6 sessions both used the same BGP router-id? As I mentioned before, if you connect these two sessions to the same peer, that peer would not have any issue accepting both sessions. 

So why do you want to force a separate router-id for the v4 and v6 session?

Regards,

[okochat18]

@Harold Ritter 
Thanks for the responses.
I finally came to terms that its not possible.

Cheers

[Harold Ritter]

You are very welcome @okochat18 . As mentioned before, although you can't configure a separate BGP router-id per address family, you can probably still achieve what you wanted to.

Regards,