IOS 12.2/12.4 L2TP incompatibility (AVP 102 Username)

Brief version: A 12.4 system cannot use an accept-dialout vpdn on a

12.2 system for modem access. See previous postings for details.

I constructed an L2TP filter to run on an intermediate host. It waits for the OCRQ packet from the 12.4 system and removes the Cisco-specific AVP 102 (Username). Everything else it forwards to the 12.2 system. This makes the connection work fine, so the (extraneous, null) Username AVP is indeed the problem.

I then made my filter change the Username AVP to some unrecognized Cisco-specific attribute. This was also handled correctly the 12.2 system and the connection worked.

Finally, I made my filter leave the AVP 102 in the packet but make the value non-null (I made it "x"). Again this made the 12.2 system happy.

Does anyone know how to convince 12.4 to omit the AVP 102 or make it non-null?

Dan Lanciani ddl@danlan.*com

In article , ddl@danlan.*com (Dan Lanciani) writes: | Brief version: A 12.4 system cannot use an accept-dialout vpdn on a | 12.2 system for modem access. See previous postings for details. | | I constructed an L2TP filter to run on an intermediate host. It | waits for the OCRQ packet from the 12.4 system and removes the | Cisco-specific AVP 102 (Username). Everything else it forwards | to the 12.2 system. This makes the connection work fine, so the | (extraneous, null) Username AVP is indeed the problem. | | I then made my filter change the Username AVP to some unrecognized | Cisco-specific attribute. This was also handled correctly the 12.2 | system and the connection worked. | | Finally, I made my filter leave the AVP 102 in the packet but make | the value non-null (I made it "x"). Again this made the 12.2 system | happy. | | Does anyone know how to convince 12.4 to omit the AVP 102 or make | it non-null?

Found it; "dialer remote-name" sets the username and appears to do little else (i.e., it doesn't override the actual remote system name).

Dan Lanciani ddl@danlan.*com