[c-nsp] Need help understanding mpls error message

[Peter Rathlev]

On Tue, 2009-05-19 at 11:57 -0400, Lobo wrote:
> I've search on Cisco's website to help understand the following message 
> but I'm not 100% clear on how to find the network/router responsible for 
> generating these error messages:
> 
> .May 19 08:39:06.235 EDT: %MPLS_PACKET-4-NOLFDSB: MPLS packet received 
> on non MPLS enabled interface Vlan101 L3 type 0x8847 label {586 0 0 255}
...
> Since it's giving multiple labels, which one should I do a "mpls 
> forwarding-table label" command on and will that point me to the 
> offending block?  FYI, Vlan101 is part of our NMS network and does not 
> have LDP enabled on it.

You probably won't be able to look it up in the FIB. As it says: You
received a MPLS tagged frame on a non MPLS interface. This frame was
probably not tagged with labels that your router assigned.

What else exists on VLAN 101? Any MPLS speakers? Is VLAN 101 a "trusted"
interface?

With a sniffer you'd be able to see the source MAC address of the
frames. Something like tcpdump with the "-e" flag will show you:

18:14:39.807669 00:19:07:73:c9:40 > 00:0b:46:5a:74:20, ethertype MPLS unicast (0x8847), length 78: MPLS (label 54, exp 0, [S], ttl 247), IP, length: 64

Then you can look up the MAC-address in the L2 FIB.

Regards,
Peter