Cisco Cisco IOS Software Release 12.2(27)SBC

To troubleshoot Layer 2 Forwarding (L2F) or Layer 2 Tunnel Protocol (L2TP) virtual private dialup 
network (VPDN) tunneling events and infrastructure, use the debug vpdn command in privileged EXEC 
mode. To disable debugging output, use the no form of this command.

debug vpdn {call {event | fsm} | error | event [disconnect] | l2tp-sequencing | l2x-data | 

l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | 
fsm}}

no debug vpdn {call {event | fsm} | error | event [disconnect] | l2tp-sequencing | l2x-data | 

l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | 
fsm}}

Privileged EXEC

Displays significant events in the VPDN call manager.

Displays significant events in the VPDN call manager finite state machine 
(fsm).

Displays VPDN errors.

Displays VPDN events.

(Optional) Displays VPDN disconnect events.

Displays significant events related to L2TP sequence numbers such as 
mismatches, resend queue flushes, and drops.

Displays errors that occur in data packets.

Displays errors that occur in protocol-specific conditions.

Displays events resulting from protocol-specific conditions.

Displays detailed information about control packets in protocol-specific 
conditions.

Displays VPDN interprocess messages.

Displays information about VPDN packets.

(Optional) Displays detailed packet information, including packet dumps.

(Optional) Displays errors that occur in packet processing.

Displays debug information about VPDN Subscriber Service Switch (SSS) 
errors.

Displays debug information about VPDN SSS events.

sss fsm

Displays debug information about the VPDN SSS fsm.

12.0(23)S

This command was integrated into Cisco IOS Release 12.0(23)S.

12.0(31)S

The output was enhanced to display messages about control channel 
authentication events.