L2TPV3 and Rapid spanning tree

pthomsett · ‎11-01-2008

Hi We have implemented a number of L2TPV3 tunnels to backhaul some wireless links, our customer would like to run rapid spanning tree over the link as there is potentially a loop, however it seems that the BPDUs are not being sent over the link...

Possibly this is because the L2TPV3 xconnect port is deployed on a switch port/VLAN as the port is provided by a switch module on a 2811 router..

Can you advise if this is normal operation or if twe can turn on or off the sending of this type of info

Giuseppe Larosa · ‎11-02-2008

Hello Paul,

I've found only this recommandation for the case of 802.1Q subinterface:

"Due to the way in which L2TPv3 handles 802.1q VLAN packets, the Ethernet interface must be configured in promiscuous mode to capture all traffic received on the Ethernet segment attached to the router. All frames are tunneled through the L2TP pseudowire."

see

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gtl2tpv3.html#wp1043064

In addition in Cisco Feature Navigator there is no specific voice for transporting STP Bpdus over L2TPv3.

What you suggest is possible: to verify this if you can build a setup with an external switch or you can use a cross-over cable to report the L2 vlan over a "router" port you could be able to see the STP Bpdus carried over L2TPv3.

In 802.1Q tunneling there are commands to be used to transport L2 protocols like STP, VTP and CDP but not in L2TPv3.

Hope to help

Giuseppe