L2TPv3 on a PE using a FR subif - possible ??

Unanswered Question
Mar 8th, 2007


When using L2TPv3 on a PE (towards the CE), does it work on FR subifs?

I am able to get it working when I use the physical/main FR intf - both static and dynamic L2TPv3 tunnels work across the MPLS core with no issues.

But when I tried to use a subif, the command line does not give me an option to specify the subif.

Is this a normal behavior or just a bug in the code? I am running 12.4(7a)Enterprise on a 3640.

Here is the error msg. that I get when I try to specify a subif in the L2TPv3 config:

PE1-R6(config)#connect L2TPV3 serial 0/0:605 ?

% Unrecognized command

PE1-R6(config)#connect L2TPV3 serial 0/0:?

<2147483647-0> Serial interface number

Subif S0/0.605 on PE1 is connected to a CE.

Thank you for your help.


I have this problem too.
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attrgautam Fri, 03/09/2007 - 04:33

You cannot specify the DLCI in this fashion. You need to specify the serial interface and DLCI seperately cause the xconnect is per interface and per DLCI, so the syntax will be

connect l2tpv3 serial0/0 605(DLCI) l2tranport

xconnect encapsulation l2tpv3

Let me know if it helps

rajju Fri, 03/09/2007 - 10:01

Yes, I do have the connect statement exactly like that.

But thanks for your help.

I finally get it.

Irrespective of if you have a subif towards the CE, the trick is NOT to specify the DLCI under the subif or the main intf.

The DLCI needs to be specified in the xconnect statement and it somehow "magically" understands it for that particular subif.

I did configure an a subif on both the CE's towards the PE's and it is all working fine now with no issues.

I can get from one CE to another !!

Thanks so much !!

Best regards.

Here are my results:

R4-CE2#sh ip route rip

R [120/1] via, 00:00:23, Serial0/0.408

R4-CE2#ping ip source

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:

Packet sent with a source address of


Success rate is 100 percent (5/5), round-trip min/avg/max = 112/113/116 ms


R8-P#sh l2tun session state

%No active L2F tunnels

L2TP Session Information Total tunnels 1 sessions 2

LocID RemID TunID Username, Intf/ State Last Chg Uniq ID

Vcid, Circuit

1450 16674 62701 608, Fa0/1 est 00:24:41 5

1451 16675 62701 2, Se0/0:804 est 00:24:29 6

%No active PPTP tunnels


R8-P#sh l2tun tunnel state

%No active L2F tunnels

L2TP Tunnel Information Total tunnels 1 sessions 2

LocID RemID Local Name Remote Name State Last-Chg

62701 507 R8-P R6-PE1 est 00:25:11

%No active PPTP tunnels



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