MPLS VRF Forwarding troubles after IOS upgrade

[ehsolnet]

After an IOS upgrade from 12.2.18S to 12.2.25S7 on a 7206VXR-NPE300 I have MPLS VRF forwarding troubles. The problem is the router doesn't label the packets anymore. I did the following for debugging:

LDP Discovery looks fine. MPLS Packet debugging show only incomming packets.

With the command "sh ip bgp vpnv4 vrf CustA>" all routes are present also with "sh ip route vrf CustA". But with "sh mpls forwarding-table vrf CustA 10.10.10.0 32" the route isn't visible.

Is there a new command which I missed ?

Thank your very much for your help.

[Harold Ritter]

First you might want to check that all your LDP sessions are (show mpls ldp nei). The default protocol has changed from TDP to LDP between 12.2(18)S and 12.2(25)S7. This might be the issue you are running into.

3 things you might also want to check:

- show ip cef for the PE from which we receive the update. This will tell you if you have a label for the other egress PE.

- show ip bgp vpn vrf CustA labels. This will tell you if you receive a label via VPNv4.

- show ip cef vrf CustA 10.10.10.10. This will tell you if you have a label stack (assuming the egress PE is not directly connected) to reach the destination address.

Hope this helps,

[ehsolnet]

I allready changed from TDP to LDP with 12.2(18)S a while ago. I also see all LDP sessions are up and connected.

- show ip cef

Doesn't show any local tag !

-show ip bgp vpn vrf CustA labels

Seems ok, I receive the prefix with an out Label and a correct Next-HOP

-show ip cef vrf CustA 10.10.10.10

-show ip cef vrf vpn600 10.10.10.10

10.10.10.0/24

nexthop GigabitEthernet2/0.550 label 1609

I'm not sure it this is correct, because all other implementations 12.4,12.2(18) give some output about tag information set.

For me it looks like the router doesn't generate local labels, this is very strange.

Thank your very much for your input.

[Harold Ritter]

A couple of things.

- Are the two PEs directly connected? If not, the show ip cef should show you a label for the egress PE.

- I'm unsure why you use two different VRFs in the commands you provided (ie: CustA and vpn600).

- The output from "show ip cef vrf vpn600 10.10.10.10" show only one label, which would indicate that the ingress and egress PEs are directly connected or that you don't receive an IGP label via LDP for the egress PE.

Hope this helps,

[ehsolnet]

Thank you for your answer:

>- Are the two PEs directly connected?

Yes, the two PEs are directly connected to a VLAN with other PE's.

[PE] ---VLAN --- [PE]

>- I'm unsure why you use two different VRFs

Sorry, this was posting fault. I checked the commands with two diffrent VRFs to verify the output.

After all debugging it looks like, the router receives the labeled packet but doesn't know the next-hop interface.

[Harold Ritter]

So if I understand correctly, you can't even ping from CE to CE, right?

According to the following show command:

-show ip cef vrf vpn600 10.10.10.10

10.10.10.0/24

nexthop GigabitEthernet2/0.550 label 1609

the label for this specific prefix is 1609. Could you please go on the egress PE and do a "show mpls for" to verify that you see an entry in the LFIB for this label.

Hope this helps,

[ehsolnet]

>So if I understand correctly, you can't even ping from CE to CE, right?

Yes, that is correct.

>Could you please go on the egress PE and do a "show mpls fo

Yes I see the label on the egress PE.

Thank you for all your help. But I just solved my problem after an upgrade to 12.4(3) without changing the configuration.

After the upgrade the command "sh ip cef vrf CustA" shows an Interface.

10.10.10.0/24 212.101.3.18 GigabitEthernet2/0.550

Maybe I missed a feature in 12.2(25)S7 :-(

Regards

Erich