1. CEF (Cisco Express Forwarding)
Since CEF are mandatory for MPLS configuration, since CEF are controll plan support where cache packet data in label switching how the MPLS can forward the MPLS Packet.
Router#show ip cef summary
IP CEF with switching (Table Version 131), flags=0x0, bits=8
32 routes, 0 reresolve, 0 unresolved (0 old, 0 new)
32 leaves, 18 nodes, 23004 bytes, 125 inserts, 93 invalidations
1 load sharing elements, 336 bytes, 1 references
universal per-destination load sharing algorithm, id B642EBCF
1 CEF resets, 6 revisions of existing leaves
6 in-place modifications
refcounts: 4909 leaf, 4864 node
Router# show ip cef
%CEF not running
Prefix Next Hop Interface
2. Verify MPLS
Router # show mpls interfaces
Interface IP Tunnel Operational
(…)
Serial1/1.1 Yes (tdp) Yes Yes
Serial1/1.2 Yes Yes No
Serial1/1.3 Yes (tdp) Yes Yes
Verify Label Distribution
Issue the show tag-switching tdp discovery command in order to display the discovered neighbors:
Router# show tag-switching tdp discovery
Local TDP Identifier:
10.10.10.3:0
Discovery Sources:
Interfaces:
Serial1/1.1 (tdp): xmit/recv
TDP Id: 10.10.10.1:0
Serial1/1.2 (tdp): xmit/recv
TDP Id: 10.10.10.2:0
Serial1/1.3 (tdp): xmit/recv
TDP Id: 10.10.10.6:0
In the show tag-switching tdp discovery command output, the use of TDP binds labels with routes. If any of the presumed neighbors is not present and you cannot ping the presumed neighbor, a connectivity problem exists and the LDP cannot run. If LDP runs correctly, it assigns one label per forwarding equivalent class.
Note: If the router ID for the LDP cannot be reached from the global routing table, the neighbor relationship fails to establish.
3. Verify Label Bindings
Router# show tag-switching tdp bindings
(…)
tib entry: 10.10.10.1/32, rev 31
local binding: tag: 18
remote binding: tsr: 10.10.10.1:0, tag: imp-null
remote binding: tsr: 10.10.10.2:0, tag: 18
remote binding: tsr: 10.10.10.6:0, tag: 21
tib entry: 10.10.10.2/32, rev 22
local binding: tag: 17
remote binding: tsr: 10.10.10.2:0, tag: imp-null
remote binding: tsr: 10.10.10.1:0, tag: 19
remote binding: tsr: 10.10.10.6:0, tag: 22
tib entry: 10.10.10.3/32, rev 2
local binding: tag: imp-null
remote binding: tsr: 10.10.10.2:0, tag: 17
remote binding: tsr: 10.10.10.1:0, tag: 20
remote binding: tsr: 10.10.10.6:0, tag: 23
tib entry: 10.10.10.4/32, rev 40
local binding: tag: 20
remote binding: tsr: 10.10.10.1:0, tag: 16
remote binding: tsr: 10.10.10.2:0, tag: 20
remote binding: tsr: 10.10.10.6:0, tag: 24
tib entry: 10.10.10.5/32, rev 44
local binding: tag: 22
remote binding: tsr: 10.10.10.1:0, tag: 17
remote binding: tsr: 10.10.10.2:0, tag: 22
remote binding: tsr: 10.10.10.6:0, tag: 25
tib entry: 10.10.10.6/32, rev 48
local binding: tag: 23
remote binding: tsr: 10.10.10.6:0, tag: imp-null
remote binding: tsr: 10.10.10.1:0, tag: 22
remote binding: tsr: 10.10.10.2:0, tag: 24
(…)
Router# show tag-switching forwarding-table 10.10.10.4 detail
Local Outgoing Prefix Bytes
tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface
20 16 10.10.10.4/32 0 Se0/1.1 point2point
MAC/Encaps=4/8, MTU=1500, Tag Stack{16}
48D18847 00010000
No output feature configured
Per-packet load-sharing
4. Verify That Labels Are Set
Use the debug mpls packet command or the MPLS-aware traceroute command functionality in order to make sure that the labels are set.
Router# traceroute 10.10.10.4
Type escape sequence to abort.
Tracing the route to 10.10.10.4
1 10.1.1.21 [MPLS: Label 20 Exp 0] 272 msec 268 msec 300 msec
2 10.1.1.5 [MPLS: Label 16 Exp 0] 228 msec 228 msec 228 msec
3 10.1.1.14 92 msec * 92 msec
5. PING
Last way we need to verify our neighboor can we reach our neigh as well?
6. BGP Route
in my case i used MP-BGP to route between PE to carry my VRF, so I need to check MP-BGP route summary status. to make sure my RD can work proper.
Router#sh ip bgp sum
BGP router identifier 1.1.1.1, local AS number 111
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
21.21.21.21 4 111 9 9 1 0 0 00:03:11 0