05-07-2008 11:26 AM
Hi,there:
We have a couple Cat6500 as our MPLS/VPN P, PE routers. But from the following first command output, we just only can see one label (VPN lable) 339 imposed,can't see the IGP label imposed.
From the second command we can see both IGP and VPN labels (339,224 or 339,20)are imposed.
Is there anybody can point out why the first command just can only show the VPN label ?
We're using Sup720 supervisor and 12.2(18)SXF9 IOS.
---
6500PE#sh ip cef vrf XYZ 172.212.0.0 255.255.0.0 detail
172.212.0.0/16, version 321, epoch 0
0 packets, 0 bytes
tag information set, all rewrites owned
local tag: VPN-route-head
fast tag rewrite with
Recursive rewrite via 172.17.0.213/32, tags imposed {339}
via 172.17.0.213, 0 dependencies, recursive
next hop 192.168.131.128, TenGigabitEthernet2/5 via 172.17.0.213/32 (Default)
valid adjacency
tag rewrite with
Recursive rewrite via 172.17.0.213/32, tags imposed {339}
Recursive load sharing using 172.17.0.213/32.
-----
-----
-----
6500PE#sh mls cef vrf XYA 172.212.0.0
Codes: decap - Decapsulation, + - Push Label
Index Prefix Adjacency
108775 172.212.0.0/16 Te2/5 339(+),224(+) (Hash: 0001)
Te1/5 339(+),20(+) (Hash: 0002)
6500PE
Solved! Go to Solution.
05-13-2008 08:46 PM
Hi Jerry,
It is only possible to see both labels with "show ip cef ..." in one command, if there is no load sharing to the BGP next hop. If there is more than one equal cost path to the BGP next hop, you need two commands to see all involved labels, just as you have observed it.
In a 6500 your "show mls ... " command is the only way I know to see both labels in one output of a show commands.
In your case, "sh ip cef 172.17.0.213 255.255.255.255 detail" will only provide you with information about the LDP labels used to reach 172.17.0.213/32. The VPN labels have nothing to do with that.
In brief:
1) IF there is only one IGP path to the BGP next hop, then "show ip cef vrf ...
2) IF there is more than one equal cost path to the BGP next hop, then "show ip cef vrf ...
As a quick check you could also use "traceroute vrf ...
Hope this helps! Please use the rating system.
Regards, Martin
05-07-2008 11:40 PM
Hi,
The observed output is due to load balancing in the MPLS core, i.e. there are several pathes to the BGP next hop known to CEF.
Have a look at the respective output statement:
--------
Recursive rewrite via 172.17.0.213/32, tags imposed {339}
Recursive load sharing using 172.17.0.213/32.
--------
To get the full label stack you need to check the CEF/LFIB entries for 172.17.0.213/32 with "show ip cef 172.17.0.213 255.255.255.255 detail" or with "show mpls forwarding-table", which will give you the values obtained by the output of your second command available on the 6500:
172.212.0.0/16
Te2/5 339(+),224(+) (Hash: 0001)
Te1/5 339(+),20(+) (Hash: 0002)
You should be able to see outgoing labels 20 and 224 for 172.17.0.213/32.
Hope this helps! Please use the rating system.
Regards, Martin
05-09-2008 06:43 AM
Hi,Martin:
Thanks for your reply.
I tried these two commands, but just only could get IGP labels(20 and 224), no way to see the VPN label(339).
Any idea ?
Jerry
--
--
6500PE#sh ip cef 172.17.0.213 255.255.255.255 detail
172.17.0.213/32, version 1080, epoch 0
0 packets, 0 bytes
tag information set, shared, all rewrites owned
local tag: 171
via 192.168.130.128, TenGigabitEthernet1/5, 11 dependencies
traffic share 1
next hop 192.168.130.128, TenGigabitEthernet1/5
valid adjacency
tag rewrite with Te1/5, 192.168.130.128, tags imposed: {20}
via 192.168.131.128, TenGigabitEthernet2/5, 43 dependencies
traffic share 1
next hop 192.168.131.128, TenGigabitEthernet2/5
valid adjacency
tag rewrite with Te2/5, 192.168.131.128, tags imposed: {224}
0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 0 packets, 0 bytes
6500PE#sh
--
--
6500PE#show mpls forwarding-table 172.17.0.213 32 detail
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
171 20 172.17.0.213/32 0 Te1/5 192.168.130.128
MAC/Encaps=14/18, MRU=1548, Tag Stack{20}
001A6C9F0A44001CF9B3D0008847 00014000
No output feature configured
Per-destination load-sharing, slots: 0 2 4 6 8 10 12 14
224 172.17.0.213/32 0 Te2/5 192.168.131.128
MAC/Encaps=14/18, MRU=1548, Tag Stack{224}
001A6C9F12BC001CF9B3D0008847 000E0000
No output feature configured
Per-destination load-sharing, slots: 1 3 5 7 9 11 13 15
6500PE#
05-13-2008 08:46 PM
Hi Jerry,
It is only possible to see both labels with "show ip cef ..." in one command, if there is no load sharing to the BGP next hop. If there is more than one equal cost path to the BGP next hop, you need two commands to see all involved labels, just as you have observed it.
In a 6500 your "show mls ... " command is the only way I know to see both labels in one output of a show commands.
In your case, "sh ip cef 172.17.0.213 255.255.255.255 detail" will only provide you with information about the LDP labels used to reach 172.17.0.213/32. The VPN labels have nothing to do with that.
In brief:
1) IF there is only one IGP path to the BGP next hop, then "show ip cef vrf ...
2) IF there is more than one equal cost path to the BGP next hop, then "show ip cef vrf ...
As a quick check you could also use "traceroute vrf ...
Hope this helps! Please use the rating system.
Regards, Martin
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