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R1#show ip bgp vpnv4 all BGP table version is 11, local router ID is 172.12.1.16 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path Route Distinguisher: 100:1 (default for vrf GREEN) i22.22.22.22/32 2.2.2.2 0 100 0 i 172.11.1.0/24 0.0.0.0 0 32768 i i172.11.2.0/24 2.2.2.2 0 100 0 i Route Distinguisher: 100:2 (default for vrf ORANGE) 172.12.1.0/24 0.0.0.0 0 32768 i i172.12.2.0/24 2.2.2.2 0 100 0 i
So lets take a Route in VRF Green
R1#traceroute vrf GREEN 22.22.22.22 Type escape sequence to abort. Tracing the route to 22.22.22.22 1 192.168.15.5 [MPLS: Labels 18/24 Exp 0] 400 msec 396 msec 400 msec 2 192.168.37.7 [MPLS: Labels 25/24 Exp 0] 356 msec 384 msec 400 msec 3 192.168.37.3 [MPLS: Labels 18/33/24 Exp 0] 324 msec 300 msec 328 msec 4 192.168.34.4 [MPLS: Labels 19/33/24 Exp 0] 308 msec 360 msec 420 msec 5 192.168.68.8 [MPLS: Labels 33/24 Exp 0] 352 msec 300 msec 300 msec 6 192.168.68.6 [MPLS: Labels 17/24 Exp 0] 332 msec 300 msec 300 msec 7 22.22.22.22 116 msec * 112 msec
Step 1: 192.168.15.5 [MPLS: Labels 18/24 Exp 0] 400 msec 396 msec 400 msec
R1#show ip bgp vpnv4 all labels Network Next Hop In label/Out label Route Distinguisher: 100:1 (GREEN) 22.22.22.22/32 2.2.2.2 nolabel/24
Looking at the BGP VPN4 we can see that the packet is labeled with label 24 in order to reach network 22.22.22.22
The VRF FIB Table indicates
R1#show ip cef vrf GREEN 22.22.22.22 22.22.22.22/32, version 9, epoch 0, cached adjacency to Serial0/0/0.101 0 packets, 0 bytes tag information set local tag: VPN-route-head fast tag rewrite with Se0/0/0.101, point2point, tags imposed: {18 24} via 2.2.2.2, 0 dependencies, recursive next hop 192.168.15.5, Serial0/0/0.101 via 2.2.2.2/32 valid cached adjacency tag rewrite with Se0/0/0.101, point2point, tags imposed: {18 24}
That we are using label 18 to reach the next hop and label 24 to reach the VPNV4 Route via R2
We can see then that to reach R2 we use label 18
R1#show mpls ldp bindings 2.2.2.2 32 tib entry: 2.2.2.2/32, rev 30 local binding: tag: 16 remote binding: tsr: 5.5.5.5:0, tag: 18
Step 2 192.168.37.7 [MPLS: Labels 25/24 Exp 0] 356 msec 384 msec 400 msec
Now the FIB table at R5
R5#show ip cef 2.2.2.2 2.2.2.2/32, version 63, epoch 0, cached adjacency to Serial0/0/0.102 0 packets, 0 bytes tag information set local tag: 18 fast tag rewrite with Se0/0/0.102, point2point, tags imposed: {25} via 192.168.57.7, 0 dependencies, recursive next hop 192.168.57.7, Serial0/0/0.102 via 192.168.57.7/32 valid cached adjacency tag rewrite with Se0/0/0.102, point2point, tags imposed: {25}
Show that R5 generate label 18, and if he receive something with label 18, he must swap it with label 25, and he sends that packet to R7 via the directly conected interface s0/0/0.102
R7#show mpls forwarding-table vrf YELLOW 2.2.2.2 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 25 18 2.2.2.2/32[V] 58997 Se0/0/0.111 point2point R7#
The same here 25 is swap with label 18
R7#show ip bgp vpnv4 all lab | in 2.2.2.2 2.2.2.2/32 8.8.8.8 nolabel/33
Step 3: 192.168.37.3 [MPLS: Labels 18/33/24 Exp 0] 324 msec 300 msec 328 msec
R7 to reach the loopback of R8, he is distributing unsolicited label 19,
R7#show ip cef 8.8.8.8 8.8.8.8/32, version 39, epoch 0, cached adjacency to Serial0/0/0.111 0 packets, 0 bytes tag information set, shared local tag: 19 fast tag rewrite with Se0/0/0.111, point2point, tags imposed: {18} via 192.168.37.3, Serial0/0/0.111, 4 dependencies next hop 192.168.37.3, Serial0/0/0.111 valid cached adjacency tag rewrite with Se0/0/0.111, point2point, tags imposed: {18} R7#
and if we receive something with 19 we swap it with label 18
Step 4: 192.168.34.4 [MPLS: Labels 19/33/24 Exp 0] 308 msec 360 msec 420 msec
at the LFIB of R3
R3#show mpls forwarding-table 8.8.8.8 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 18 19 8.8.8.8/32 220979 Se0/0/0.112 point2point
We can determine that he is swapping label 18 with 19
Step 5: 192.168.68.8 [MPLS: Labels 33/24 Exp 0] 352 msec 300 msec 300 msec
At the LFIB of R4
R4#show mpls forwarding-table 8.8.8.8 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 19 Pop tag 8.8.8.8/32 215211 Se0/0/0.111 point2point
19 is poped and send it as a label packet with 2 labels.
Step 6: 192.168.68.6 [MPLS: Labels 17/24 Exp 0] 332 msec 300 msec 300 msec
R8, is generating label 17
R8#show mpls forwarding-table vrf YELLOW 2.2.2.2 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 33 17 2.2.2.2/32[V] 64537 Se0/0/0.112 point2point
and is sending this to R6
R6#show mpls forwarding-table 2.2.2.2 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 17 Pop tag 2.2.2.2/32 64164 Se0/0/0.101 point2point
Step 7: 22.22.22.22 116 msec * 112 msec
R2 now remove the upper label
R2#show mpls forwarding-table Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 16 16 1.1.1.1/32 0 Se0/0/0.101 point2point 17 19 5.5.5.5/32 0 Se0/0/0.101 point2point 18 18 192.168.15.0/24 0 Se0/0/0.101 point2point 19 20 192.168.57.0/24 0 Se0/0/0.101 point2point 20 Pop tag 6.6.6.6/32 0 Se0/0/0.101 point2point 21 Pop tag 192.168.68.0/24 0 Se0/0/0.101 point2point 22 Aggregate 172.12.2.0/24[V] 0 23 Aggregate 172.11.2.0/24[V] 26792 24 Aggregate 22.22.22.22/32[V] 9576
and 24 here is the label that R1 use at the VPVN4 label
R2#show mpls forwarding-table vrf GREEN 22.22.22.22 Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 24 Aggregate 22.22.22.22/32[V] 9576
the label operation by
http://www.ciscopress.com/articles/article.asp?p=680824
is as follows:
Pop: The top label is removed. The packet is forwarded with the remaining label stack or as an unlabeled packet.
Swap: The top label is removed and replaced with a new label.
Push: The top label is replaced with a new label (swapped), and one or more labels are added
(pushed) on top of the swapped label.
Untagged/No Label: The stack is removed, and the packet is forwarded unlabeled.
Aggregate: The label stack is removed, and an IP lookup is done on the IP packet.
Nice Site!
http://google.com
Hi Victor,
I’m in the middle of nowhere looking for Tags Imposed means.
And this great post help me a lot.
Specially your how to steps to read mpls verifications.