InterAS Option B - ASBR interfaces not being MPLS enabled

[steven.crutchley]

Hi everyone,

I'm labbing inter-AS Option B, and I keep running into a problem whereby the control plane is working (routes are being exchanged correctly between ASNs) but the external interfaces (ASBR to ASBR NNIs) are not enabled with MPLS until I shut/no shut them. 

For example, ASBR1 (in AS 100) is connected to ASBR2 (in AS 200) with Gi0/0/0/2. If I issue `show mpls interfaces` I get the following:

RP/0/RP0/CPU0:ASBR1#show mpls interfaces 
Sat Feb  8 17:43:19.708 UTC
Interface                  LDP      Tunnel   Static   Enabled 
-------------------------- -------- -------- -------- --------
GigabitEthernet0/0/0/0     Yes      No       No       Yes
GigabitEthernet0/0/0/4     No       No       No       Yes
GigabitEthernet0/0/0/1     Yes      No       No       Yes
RP/0/RP0/CPU0:ASBR1#

So Gi0/0/0/2 in not MPLS enabled. 

To fix this, I simply do this:

RP/0/RP0/CPU0:ASBR1#conf t
Sat Feb  8 17:45:49.283 UTC
RP/0/RP0/CPU0:ASBR1(config)#interface gigabitEthernet 0/0/0/2
RP/0/RP0/CPU0:ASBR1(config-if)#shut
RP/0/RP0/CPU0:ASBR1(config-if)#commit
Sat Feb  8 17:45:54.972 UTC
RP/0/RP0/CPU0:ASBR1(config-if)#no shut
RP/0/RP0/CPU0:ASBR1(config-if)#commit
Sat Feb  8 17:46:12.747 UTC
LC/0/0/CPU0:Feb  8 17:46:12.856 UTC: ifmgr[324]: %PKT_INFRA-LINK-3-UPDOWN : Interface GigabitEthernet0/0/0/2, changed state to Down 
RP/0/RP0/CPU0:ASBR1(config-if)#LC/0/0/CPU0:Feb  8 17:46:13.480 UTC: ifmgr[324]: %PKT_INFRA-LINK-3-UPDOWN : Interface GigabitEthernet0/0/0/2, changed state to Up 

RP/0/RP0/CPU0:ASBR1(config-if)#
RP/0/RP0/CPU0:ASBR1(config-if)#
RP/0/RP0/CPU0:ASBR1(config-if)#
RP/0/RP0/CPU0:ASBR1(config-if)#
^XRP/0/RP0/CPU0:ASBR1#sh mpls interfaces   
Sat Feb  8 17:46:23.230 UTC
Interface                  LDP      Tunnel   Static   Enabled 
-------------------------- -------- -------- -------- --------
GigabitEthernet0/0/0/0     Yes      No       No       Yes
GigabitEthernet0/0/0/4     No       No       No       Yes
GigabitEthernet0/0/0/2     No       No       No       Yes
GigabitEthernet0/0/0/1     Yes      No       No       Yes
RP/0/RP0/CPU0:ASBR1#

Then all of my traces and pings work ok. 

Has anyone seen anything like this or know why this is happening? 

Could is be the order that I configure things or the OS version that I'm using (xrv9k 7.9.2).

Thanks in advance for any help.

[Harold Ritter]

Hi @steven.crutchley ,

Not something I have come across. Can you please provide the output for the following commands from both asbrs:

show runn interface gi0/0/0/2

show runn router static

Regards,

[steven.crutchley]

This is what I've configured on the NNI to the next ISP:

RP/0/RP0/CPU0:ASBR1#sh run interface gigabitEthernet 0/0/0/2
Sat Feb 15 18:39:36.789 UTC
interface GigabitEthernet0/0/0/2
 description link to ISP2-ASBR1
 ipv4 address 10.1.1.1 255.255.255.0
!

RP/0/RP0/CPU0:ASBR1#sh run router static
Sat Feb 15 18:39:48.026 UTC
router static
 address-family ipv4 unicast
  10.1.1.2/32 GigabitEthernet0/0/0/2
 !
!

RP/0/RP0/CPU0:ASBR1#

The /32 static is all there. 

This is a difficult one to replicate. I've just reconfigured everything from scratch and it has worked ok without the need to shut/unshut. I think it might be something to do with the order in which I apply the commands but I can't figure out the exact sequence that causes it. It's happened several times though. 

[MHM Cisco World]

Sequence is make IGP sync first then apply mpls command with take care of router-id mpls use.

Router-id must reachable before mpls is established.

To solve this issue permanent use mpls igp sync 

MHM