QinQ over QinQ including L2TP

iftikhar.qurashi · ‎08-01-2007

I have hit a scenario and looking for some techincal help here for any possible work arounds if you have seen similar thing somewhere else. Following is the simplified topology

CustomerSwitch1(dot1q)------------(qinq,l2tp)SP-A Switch1(dot1q)-----------------(qinq,l2tp)SP-BSwitch1(dot1q)----------------------------(dot1q)SP-BSwitch2(qinq,l2tp)----------------------(dot1q)SP-ASwitch2(qinq,l2tp)----------------(dot1q)CustomerSwitch2

The problem I saw was SP-BSwitch1 port facing SP-ASwitch1 goes into error disable state due to L2TP gurad.

The reason as defined by L2TP gurad reference is as follows

"The interface goes to errdisabled state, If an encapsulated PDU (with the proprietary destination MAC address) is received from a tunnel port or access port with Layer 2 tunneling enabled, the tunnel port is shut down to prevent loops"

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml

I do not want to disable L2TP gurad in SP-B cloud as this feature avoid loop creation, Is there any other way to handle this problem, please let me know

smahbub · ‎08-07-2007

I think you have to disable L2TP gurad in SP-B cloud. A configuration issue, such as a speed and duplex mismatch and a performance issue, such as an oversubscription may be creating problem.