Labeled unicast enable in option b?

[Ignacho]

Hi guys, 

When i configure the option b BGP on my ASR 9006 i need to enable the labeled unicast in BGP to the neighbor to see the mpls interface enable in the router, this ASBR is PE/RR inline too. Then I eliminate the labeled-unicast but the mpls interface doesn't down, is continue up but if the router reboot, the mpls interface doesn't appear, why happen this situation? The other neighbor is a Juniper ASBR, I appreciate your suggestion about that.

Regards,

Ignacho

[Harold Ritter]

Hi @Ignacho ,

You do not need to configure bgp lu towards the other asbr to see mpls enabled on the interface. You need to config a static host route as follow:

For example, you have a p2p link between the two asbrs. You have 192.168.12.1/24 configured on gi0/0/0/0 on your side and 192.168.12.2/24 configured on the other side and you use 192.168.12.2 as the bgp neighbor with address-family vpnv4 on your side. You would configure the following static host route on your asbr:

router static

address-family ipv4 unicast

192.168.12.2/32 gi0/0/0/0

With this static route configured, you should see gi0/0/0/0 when you do a "show mpls interface".

Regards,

[Ignacho]

Hi Harold,

This is the configuration:

router bgp XXXX
nsr
bgp router-id 10.11.0.205
bgp graceful-restart restart-time 120
mpls activate
interface GigabitEthernet0/3/0/18.2100
!

router static
maximum path ipv4 140000
address-family ipv4 unicast
10.10.5.2/32 GigabitEthernet0/3/0/18.2100 10.10.5.2

router bgp XXXX
neighbor 10.10.5.2
remote-as XXXX
bfd fast-detect
bfd multiplier 3
bfd minimum-interval 300
description ASBR
local address 10.10.5.1
address-family vpnv4 unicast
route-reflector-client
next-hop-self
!

Don't appear the interface in mpls:

show mpls interfaces

Interface LDP Tunnel Static Enabled
-------------------------- -------- -------- -------- --------
GigabitEthernet0/3/0/18.2002 Yes No No Yes
GigabitEthernet0/3/0/18.2004 Yes No No Yes

Our case is special because in our networks we have used the same AS, these ASBRs need to be RRinline too.

Regards,

Ignacho.

[MHM Cisco World]

Same AS is not use inter-AS (except case that we use confedental bgp) it use seamless mpls

https://www.linkedin.com/pulse/unifiedseamless-mpls-nelson-paiva

MHM

[Harold Ritter]

Hi @MHM Cisco World ,

Seamless MPLS uses InterAS option C, not option B.

Regards,

[Harold Ritter · Accepted solution]

Hi @Ignacho ,

Your initial description was misleading. Option B, as described by section 10 of RFC4364 has to be between two different ASes. 

https://datatracker.ietf.org/doc/html/rfc4364#section-10

Your scenario is very different and not commonly seen as it is in the scope of a single AS. eBGP vpnv4 will not work for you in this scenario and for ibgp vpnv4 to work between your two ASBRs (which are not really ASBRs per say) you will need to run ibgp ipv4+label (bgp-lu) between them to get the inter "ASBR" interface to be mpls activated.

This should allow vpnv4 to work properly.

Regards,