MPLS Troubleshooting

MPLS Basic Troubleshooting

1) Is CEF enabled? This is a pre-requisite for MPLS.

show ip cef summary

On Router 1 where CEF is explicitly disabled....

Router_1#s ip cef sum
IP CEF without switching (Table Version 15), flags=0x0
4294967293 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 0
0 leaves, 0 nodes, 0 bytes, 18 inserts, 18 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id 1D530DA6
2(1) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts: 0 leaf, 0 node

Table epoch: 0

%CEF not running

On Router 2 with cef globally enabled....

Router_2#show ip cef summ
IP CEF with switching (Table Version 11), flags=0x0
10 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 0
13 leaves, 14 nodes, 16328 bytes, 14 inserts, 1 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id 0CFD412D
2(0) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts: 3851 leaf, 3840 node

Table epoch: 0 (13 entries at this epoch)

Adjacency Table has 1 adjacency


2) Is MPLS enabled?

On Router 1 where MPLS is NOT enabled....

Router_1#show mpls for
Tag switching is not operational.
CEF or tag switching has not been enabled.
No TFIB currently allocated.

and on Router 3 where MPLS is enabled....

Router_3#show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Untagged 150.1.4.4/32 0 Fa0/0 192.168.34.4
17 Untagged 192.168.45.0/24 0 Fa0/0 192.168.34.4
18 Untagged 150.1.1.0/24[V] 0 Se2/1 point2point
19 Aggregate 192.168.13.0/24[V] \
0



3) Is MPLS enabled on all required interfaces?

Normally MPLS will be enabled on all links between core routers and disabled on links connecting to insecure devices.

Router_3#show mpls int
Interface IP Tunnel Operational
FastEthernet0/0 Yes (tdp) No Yes