To troubleshoot Layer 2 Forwarding (L2F) or Layer 2 Tunnel Protocol (L2TP) virtual private dial-up network (VPDN) tunneling
events and infrastructure, use the
debug
vpdn command in privileged EXEC mode. To disable the debugging of L2TP VPDN tunneling events and infrastructure, use the
no form of this command.
Note |
Effective with Cisco IOS Release 12.4(11)T, the L2F protocol is not supported in Cisco IOS software.
|
Cisco IOS Release 12.2(33)XNA and Later Releases
debug vpdn {call {event | fsm} | authorization {error | event} | error | event [ disconnect
[traceback]] | l2tp-sequencing | l2x-data | l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | fsm} | subscriber {error | event | fsm}}
no debug vpdn {call {event | fsm} | authorization {error | event} | error | event [ disconnect
[traceback]] | l2tp-sequencing | l2x-data | l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | fsm} | subscriber {error | event | fsm}}
Cisco IOS Releases Prior to 12.2(33)XNA
debug vpdn {call {event | fsm} | authorization {error | event} | error | event [ disconnect] | l2tp-sequencing | l2x-data | l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | fsm} | subscriber {error | event | fsm}}
no debug vpdn {call {event | fsm} | authorization {error | event} | error | event [ disconnect] | l2tp-sequencing | l2x-data | l2x-errors | l2x-events | l2x-packets | message | packet [detail | errors] | sss {error | event | fsm} | subscriber {error | event | fsm}}
Syntax Description
call
event
|
Displays significant events in the VPDN call manager.
|
call
fsm
|
Displays significant events in the VPDN call manager finite state machine (FSM).
|
authorization
error
|
Displays authorization errors.
|
authorization
event
|
Displays authorization events.
|
error
|
Displays VPDN errors.
|
event
|
Displays VPDN events.
|
disconnect
|
(Optional) Displays VPDN disconnect events.
Note
|
The
disconnect keyword is required in Cisco IOS Release 12.2(33)XNA and later releases.
|
|
traceback
|
(Optional) Displays traceback messages that provide reasons for VPDN disconnect.
|
l2tp-sequencing
|
Displays significant events related to L2TP sequence numbers such as mismatches, resend queue flushes, and drops.
|
l2x-data
|
Displays errors that occur in data packets.
|
l2x-errors
|
Displays errors that occur in protocol-specific conditions.
|
l2x-events
|
Displays events resulting from protocol-specific conditions.
|
l2x-packets
|
Displays detailed information about control packets in protocol-specific conditions.
|
message
|
Displays VPDN interprocess messages.
|
packet
|
Displays information about VPDN packets.
|
detail
|
(Optional) Displays detailed packet information, including packet dumps.
|
errors
|
(Optional) Displays errors that occur in packet processing.
|
sss
error
|
Displays debug information about VPDN Subscriber Service Switch (SSS) errors.
|
sss
event
|
Displays debug information about VPDN SSS events.
|
sss
fsm
|
Displays debug information about the VPDN SSS FSM.
|
subscriber
error
|
Displays debug information about VPDN Subscriber errors.
|
subscriber
event
|
Displays debug information about VPDN Subscriber events.
|
subscriber
fsm
|
Displays debug information about the VPDN Subscriber FSM.
|
Command Modes
Privileged EXEC (#)
Command History
Release
|
Modification
|
11.2 T
|
This command was introduced.
|
12.0(5)T
|
This command was modified. Support was added for L2TP debugging messages. The
l2tp-sequencing
and
error keywords were added. The
l2f-errors ,
l2f-events , and
l2f-packets keywords were changed to
l2x-errors ,
l2x-events , and
l2x-packets .
|
12.2(4)T
|
This command was modified. The
call ,
event ,
fsm , and
message keywords were added.
|
12.2(11)T
|
This command was modified. The
detail keyword was added.
|
12.0(23)S
|
This command was integrated into Cisco IOS Release 12.0(23)S.
|
12.2(13)T
|
This command was modified. The
sss ,
error ,
event , and
fsm keywords were added.
|
12.3(14)T
|
This command was modified. Support was added to decode the outbound control channel authentication events.
|
12.0(31)S
|
This command was modified. The output was enhanced to display messages about control channel authentication events.
|
12.2(27)SBC
|
This command was modified. Support for enhanced display of messages about control channel authentication events was added.
|
12.2(28)SB
|
This command was modified. Support for the display of messages about congestion avoidance events was added.
|
12.2(31)SB
|
This command was modified. Support was added to decode the outbound control channel authentication events.
|
12.4(15)T
|
This command was modified. The
authorization ,
error , and
event keywords were added.
|
12.2(33)XNA
|
This command was modified. The
traceback keyword was added.
|
12.4(20)T
|
This command was modified. The
subscriber keyword was added and the
sss keyword was removed.
|
Cisco IOS XE Release 2.6
|
This command was modified. Authentication failure messages for L2TPv3 were added.
|
Usage Guidelines
The
debug
vpdn
packet and
debug
vpdn
packet
detail commands generate several debug operations per packet. Depending on the L2TP traffic pattern, these commands may cause the
CPU load to increase to a high level that impacts performance.
Examples
The following example shows the VPDN configuration on a network access server (NAS):
vpdn-group 1
request-dialin
protocol l2f
domain example.com
initiate-to ip 172.17.33.125
username nas1 password nas1
The following is sample output from the
debug
vpdn
event command on a NAS when an L2F tunnel is brought up and Challenge Handshake Authentication Protocol (CHAP) authentication of
the tunnel succeeds:
Device# debug vpdn event
%LINK-3-UPDOWN: Interface Async6, changed state to up
*Mar 2 00:26:05.537: looking for tunnel — example.com —
*Mar 2 00:26:05.545: Async6 VPN Forwarding...
*Mar 2 00:26:05.545: Async6 VPN Bind interface direction=1
*Mar 2 00:26:05.553: Async6 VPN vpn_forward_user user6@example.com is forwarded
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to up
*Mar 2 00:26:06.289: L2F: Chap authentication succeeded for nas1.
The following is sample output from the
debug
vpdn
event command on a NAS when the L2F tunnel is brought down normally:
Device# debug vpdn event
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to down
%LINK-5-CHANGED: Interface Async6, changed state to reset
*Mar 2 00:27:18.865: Async6 VPN cleanup
*Mar 2 00:27:18.869: Async6 VPN reset
*Mar 2 00:27:18.873: Async6 VPN Unbind interface
%LINK-3-UPDOWN: Interface Async6, changed state to down
The table below describes the significant fields shown in the two previous displays. The output describes normal operations
when an L2F tunnel is brought up or down on a NAS.
Table 1. debug vpdn event Field Descriptions for the NAS
Field
|
Description
|
Asynchronous interface coming up
|
%LINK-3-UPDOWN: Interface Async6, changed state to up
|
Asynchronous interface 6 came up.
|
looking for tunnel — example.com —
Async6 VPN Forwarding...
|
Domain name is identified.
|
Async6 VPN Bind interface direction=1
|
Tunnel is bound to the interface. These are the direction values:
|
Async6 VPN vpn_forward_user user6@example.com is forwarded
|
Tunnel for the specified user and domain name is forwarded.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to up
|
Line protocol is up.
|
L2F: Chap authentication succeeded for nas1.
|
Tunnel was authenticated with the tunnel password nas1.
|
Virtual access interface coming down
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to down
|
Normal operation when the virtual access interface is taken down.
|
Async6 VPN cleanup
Async6 VPN reset
Async6 VPN Unbind interface
|
Normal cleanup operations performed when the line or virtual access interface goes down.
|
Examples
The following example shows the VPDN configuration on a tunnel server, which uses
nas1 as the tunnel name and the tunnel authentication name. The tunnel authentication name can be entered in a user’s file on
an authentication, authorization, and accounting (AAA) server and used to define authentication requirements for the tunnel.
vpdn-group 1
accept-dialin
protocol l2f
virtual-template 1
terminate-from hostname nas1
The following is sample output from the
debug
vpdn
event command on a tunnel server when an L2F tunnel is brought up successfully:
Device# debug vpdn event
L2F: Chap authentication succeeded for nas1.
Virtual-Access3 VPN Virtual interface created for user6@example.com
Virtual-Access3 VPN Set to Async interface
Virtual-Access3 VPN Clone from Vtemplate 1 block=1 filterPPP=0
%LINK-3-UPDOWN: Interface Virtual-Access3, changed state to up
Virtual-Access3 VPN Bind interface direction=2
Virtual-Access3 VPN PPP LCP accepted sent & rcv CONFACK
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access3, changed state to up
The following is sample output from the
debug
vpdn
event command on a tunnel server when an L2F tunnel is brought down normally:
Device# debug vpdn event
%LINK-3-UPDOWN: Interface Virtual-Access3, changed state to down
Virtual-Access3 VPN cleanup
Virtual-Access3 VPN reset
Virtual-Access3 VPN Unbind interface
Virtual-Access3 VPN reset
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access3, changed state to down
The table below describes the fields shown in two previous outputs. The output describes normal operations when an L2F tunnel
is brought up or down on a tunnel server.
Table 2. debug vpdn event Field Descriptions
Field
|
Description
|
L2F: Chap authentication succeeded for nas1.
|
PPP CHAP authentication status for the tunnel named
nas1 .
|
Virtual-Access3 VPN Virtual interface created for user6@example.com
|
Virtual access interface was set up on a tunnel server for the user user6@example.com.
|
Virtual-Access3 VPN Set to Async interface
|
Virtual access interface 3 was set to asynchronous for character-by-character transmission.
|
Virtual-Access3 VPN Clone from Vtemplate 1 block=1 filterPPP=0
|
Virtual template 1 was applied to virtual access interface 3.
|
%LINK-3-UPDOWN: Interface Virtual-Access3, changed state to up
|
Link status is set to up.
|
Virtual-Access3 VPN Bind interface direction=2
|
Tunnel is bound to the interface. These are the direction values:
|
Virtual-Access3 VPN PPP LCP accepted sent & rcv CONFACK
|
PPP link control protocol (LCP) configuration settings (negotiated between the remote client and the NAS) were copied to
the tunnel server and acknowledged.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access3, changed state to up
|
Line protocol is up; the line can be used.
|
%LINK-3-UPDOWN: Interface Virtual-Access3, changed state to down
|
Virtual access interface is coming down.
|
Virtual-Access3 VPN cleanup
Virtual-Access3 VPN reset
Virtual-Access3 VPN Unbind interface
Virtual-Access3 VPN reset
|
Device is performing normal cleanup operations when a virtual access interface used for an L2F tunnel comes down.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access3, changed state to down
|
Line protocol is down for virtual access interface 3; the line cannot be used.
|
Examples
The following is sample output from the
debug
vpdn
event
disconnect
traceback command on a tunnel server when an L2TP Network Server (LNS) tunnel session is disconnected:
Device# debug vpdn event disconnect traceback
*Aug 8 07:13:56.795: VPDN Vi2.1 disconnect (L2X) IETF: 18/host-request Ascend: 66/VPDN Local PPP Disconnect
*Aug 8 07:13:56.795: VPDN Vi2.1 vpdn shutdown session, result=2, error=6, vendor_err=0, syslog_error_code=2, syslog_key_type=1
*Aug 8 07:13:56.795: VPDN Vi2.1 VPDN/AAA: accounting stop sent
*Aug 8 07:13:56.795: VPDN Vi2.1 Unbinding session from idb, informational traceback:
*Aug 8 07:13:56.795: -Traceback= DFFFE7z 30EE221z 30DFBA8z 30E2F26z 30DF1DCz 30DF12Fz 1F0170Fz 1F015A1z 31E695Bz 31E674Dz 1F019F6z
*Aug 8 07:13:56.795: Vi2.1 VPDN: Resetting interface, informational traceback below:
LNS#
*Aug 8 07:13:56.795: -Traceback= DFFFE7z 30EDE74z 30EE2D4z 37996B7z 37A3019z 30EE408z 30DFBB3z 30E2F26z 30DF1DCz 30DF12Fz 1F0170Fz 1F015A1z 31E695Bz 31E674Dz 1F019F6z
Examples
The following is sample output from the
debug
vpdn
event command on the NAS when an L2TP tunnel is brought up successfully:
Device# debug vpdn event
20:19:17: L2TP: I SCCRQ from ts1 tnl 8
20:19:17: L2X: Never heard of ts1
20:19:17: Tnl 7 L2TP: New tunnel created for remote ts1, address 172.21.9.4
20:19:17: Tnl 7 L2TP: Got a challenge in SCCRQ, ts1
20:19:17: Tnl 7 L2TP: Tunnel state change from idle to wait-ctl-reply
20:19:17: Tnl 7 L2TP: Got a Challenge Response in SCCCN from ts1
20:19:17: Tnl 7 L2TP: Tunnel Authentication success
20:19:17: Tnl 7 L2TP: Tunnel state change from wait-ctl-reply to established
20:19:17: Tnl 7 L2TP: SM State established
20:19:17: Tnl/Cl 7/1 L2TP: Session FS enabled
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from idle to wait-for-tunnel
20:19:17: Tnl/Cl 7/1 L2TP: New session created
20:19:17: Tnl/Cl 7/1 L2TP: O ICRP to ts1 8/1
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from wait-for-tunnel to wait-connect
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from wait-connect to established
20:19:17: Vi1 VPDN: Virtual interface created for example1@example.com
20:19:17: Vi1 VPDN: Set to Async interface
20:19:17: Vi1 VPDN: Clone from Vtemplate 1 filterPPP=0 blocking
20:19:18: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
20:19:18: Vi1 VPDN: Bind interface direction=2
20:19:18: Vi1 VPDN: PPP LCP accepting rcv CONFACK
20:19:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
Examples
The following is sample output from the
debug
vpdn
event command on a tunnel server when an L2TP tunnel is brought up successfully:
Device# debug vpdn event
20:47:33: %LINK-3-UPDOWN: Interface Async7, changed state to up
20:47:35: As7 VPDN: Looking for tunnel — example.com —
20:47:35: As7 VPDN: Get tunnel info for example.com with NAS nas1, IP 172.21.9.13
20:47:35: As7 VPDN: Forward to address 172.21.9.13
20:47:35: As7 VPDN: Forwarding...
20:47:35: As7 VPDN: Bind interface direction=1
20:47:35: Tnl/Cl 8/1 L2TP: Session FS enabled
20:47:35: Tnl/Cl 8/1 L2TP: Session state change from idle to wait-for-tunnel
20:47:35: As7 8/1 L2TP: Create session
20:47:35: Tnl 8 L2TP: SM State idle
20:47:35: Tnl 8 L2TP: Tunnel state change from idle to wait-ctl-reply
20:47:35: Tnl 8 L2TP: SM State wait-ctl-reply
20:47:35: As7 VPDN: example1@example.com is forwarded
20:47:35: Tnl 8 L2TP: Got a challenge from remote peer, nas1
20:47:35: Tnl 8 L2TP: Got a response from remote peer, nas1
20:47:35: Tnl 8 L2TP: Tunnel Authentication success
20:47:35: Tnl 8 L2TP: Tunnel state change from wait-ctl-reply to established
20:47:35: Tnl 8 L2TP: SM State established
20:47:35: As7 8/1 L2TP: Session state change from wait-for-tunnel to wait-reply
20:47:35: As7 8/1 L2TP: Session state change from wait-reply to established
20:47:36: %LINEPROTO-5-UPDOWN: Line protocol on Interface Async7, changed state to up
Examples
The following is sample output from the
debug
vpdn
l2x-events command on the NAS when an L2F tunnel is brought up successfully:
Device# debug vpdn l2x-events
%LINK-3-UPDOWN: Interface Async6, changed state to up
*Mar 2 00:41:17.365: L2F Open UDP socket to 172.21.9.26
*Mar 2 00:41:17.385: L2F_CONF received
*Mar 2 00:41:17.389: L2F Removing resend packet (type 1)
*Mar 2 00:41:17.477: L2F_OPEN received
*Mar 2 00:41:17.489: L2F Removing resend packet (type 2)
*Mar 2 00:41:17.493: L2F building nas2gw_mid0
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to up
*Mar 2 00:41:18.613: L2F_OPEN received
*Mar 2 00:41:18.625: L2F Got a MID management packet
*Mar 2 00:41:18.625: L2F Removing resend packet (type 2)
*Mar 2 00:41:18.629: L2F MID synced NAS/HG Clid=7/15 Mid=1 on Async6
The following is sample output from the
debug
vpdn
l2x-events command on a NAS when an L2F tunnel is brought down normally:
Device# debug vpdn l2x-events
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to down
%LINK-5-CHANGED: Interface Async6, changed state to reset
*Mar 2 00:42:29.213: L2F_CLOSE received
*Mar 2 00:42:29.217: L2F Destroying mid
*Mar 2 00:42:29.217: L2F Removing resend packet (type 3)
*Mar 2 00:42:29.221: L2F Tunnel is going down!
*Mar 2 00:42:29.221: L2F Initiating tunnel shutdown.
*Mar 2 00:42:29.225: L2F_CLOSE received
*Mar 2 00:42:29.229: L2F_CLOSE received
*Mar 2 00:42:29.229: L2F Got closing for tunnel
*Mar 2 00:42:29.233: L2F Removing resend packet
*Mar 2 00:42:29.233: L2F Closed tunnel structure
%LINK-3-UPDOWN: Interface Async6, changed state to down
*Mar 2 00:42:31.793: L2F Closed tunnel structure
*Mar 2 00:42:31.793: L2F Deleted inactive tunnel
The table below describes the fields shown in the displays.
Table 3. debug vpdn l2x-events Field Descriptions—NAS
Field
|
Descriptions
|
%LINK-3-UPDOWN: Interface Async6, changed state to up
|
Asynchronous interface came up normally.
|
L2F Open UDP socket to 172.21.9.26
|
L2F opened a User Datagram Protocol (UDP) socket to the tunnel server IP address.
|
L2F_CONF received
|
L2F_CONF signal was received. When sent from the tunnel server to the NAS, an L2F_CONF indicates the tunnel server’s recognition
of the tunnel creation request.
|
L2F Removing resend packet (type ...)
|
Removing the resend packet for the L2F management packet.
There are two resend packets that have different meanings in different states of the tunnel.
|
L2F_OPEN received
|
L2F_OPEN management message was received, indicating that the tunnel server accepted the NAS configuration of an L2F tunnel.
|
L2F building nas2gw_mid0
|
L2F is building a tunnel between the NAS and the tunnel server using the multiplex ID (MID) MID0.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to up
|
Line protocol came up. Indicates whether the software processes that handle the line protocol regard the interface as usable.
|
L2F_OPEN received
|
L2F_OPEN management message was received, indicating that the tunnel server accepted the NAS configuration of an L2F tunnel.
|
L2F Got a MID management packet
|
MID management packets are used to communicate between the NAS and the tunnel server.
|
L2F MID synced NAS/HG Clid=7/15 Mid=1 on Async6
|
L2F synchronized the client IDs on the NAS and the tunnel server, respectively. An MID is assigned to identify this connection
in the tunnel.
|
Tunnel coming down
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async6, changed state to down
|
Line protocol came down. Indicates whether the software processes that handle the line protocol regard the interface as usable.
|
%LINK-5-CHANGED: Interface Async6, changed state to reset
|
Interface was marked as reset.
|
L2F_CLOSE received
|
NAS received a request to close the tunnel.
|
L2F Destroying mid
|
Connection identified by the MID is being taken down.
|
L2F Tunnel is going down!
|
Advisory message about impending tunnel shutdown.
|
L2F Initiating tunnel shutdown.
|
Tunnel shutdown has started.
|
L2F_CLOSE received
|
NAS received a request to close the tunnel.
|
L2F Got closing for tunnel
|
NAS began tunnel closing operations.
|
%LINK-3-UPDOWN: Interface Async6, changed state to down
|
Asynchronous interface was taken down.
|
L2F Closed tunnel structure
|
NAS closed the tunnel.
|
L2F Deleted inactive tunnel
|
Now-inactivated tunnel was deleted.
|
Examples
The following is sample output from the
debug
vpdn
l2x-events command on a tunnel server when an L2F tunnel is created:
Device# debug vpdn l2x-events
L2F_CONF received
L2F Creating new tunnel for nas1
L2F Got a tunnel named nas1, responding
L2F Open UDP socket to 172.21.9.25
L2F_OPEN received
L2F Removing resend packet (type 1)
L2F_OPEN received
L2F Got a MID management packet
%LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
The following is sample output from the
debug
vpdn
l2x-events command on a tunnel server when the L2F tunnel is brought down normally:
Device# debug vpdn l2x-events
L2F_CLOSE received
L2F Destroying mid
L2F Removing resend packet (type 3)
L2F Tunnel is going down!
L2F Initiating tunnel shutdown.
%LINK-3-UPDOWN: Interface Virtual-Access1, changed state to down
L2F_CLOSE received
L2F Got closing for tunnel
L2F Removing resend packet
L2F Removing resend packet
L2F Closed tunnel structure
L2F Closed tunnel structure
L2F Deleted inactive tunnel
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to down
The table below describes the significant fields shown in the displays.
Table 4. debug vpdn l2x-events Field Descriptions—Tunnel Server
Field
|
Description
|
L2F_CONF received
|
L2F configuration is received from the NAS. When sent from a NAS to a tunnel server, the L2F_CONF is the initial packet in
the conversation.
|
L2F Creating new tunnel for nas1
|
Tunnel named nas1 is being created.
|
L2F Got a tunnel named nas1, responding
|
Tunnel server is responding.
|
L2F Open UDP socket to 172.21.9.25
|
Opening a socket to the NAS IP address.
|
L2F_OPEN received
|
L2F_OPEN management message was received, indicating that the NAS is opening an L2F tunnel.
|
L2F Removing resend packet (type 1)
|
Removing the resend packet for the L2F management packet.
The two resend packet types have different meanings in different states of the tunnel.
|
L2F Got a MID management packet
|
L2F MID management packets are used to communicate between the NAS and the tunnel server.
|
%LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
|
Tunnel server is bringing up virtual access interface 1 for the L2F tunnel.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
|
Line protocol is up. The line can be used.
|
Tunnel coming down
|
L2F_CLOSE received
|
NAS or tunnel server received a request to close the tunnel.
|
L2F Destroying mid
|
Connection identified by the MID is being taken down.
|
L2F Removing resend packet (type 3)
|
Removing the resend packet for the L2F management packet.
There are two resend packets that have different meanings in different states of the tunnel.
|
L2F Tunnel is going down!
L2F Initiating tunnel shutdown.
|
Device is performing normal operations when a tunnel is coming down.
|
%LINK-3-UPDOWN: Interface Virtual-Access1, changed state to down
|
The virtual access interface is coming down.
|
L2F_CLOSE received
L2F Got closing for tunnel
L2F Removing resend packet
L2F Removing resend packet
L2F Closed tunnel structure
L2F Closed tunnel structure
L2F Deleted inactive tunnel
|
Device is performing normal cleanup operations when the tunnel is being brought down.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to down
|
Line protocol is down; virtual access interface 1 cannot be used.
|
Examples
The following partial example of the
debug
vpdn
l2x-events command is useful for monitoring a network running the L2TP Congestion Avoidance feature. The report shows that the congestion
window (Cwnd) has been reset to 1 because of packet retransmissions:
Device# debug vpdn l2x-events
.
.
.
*Jul 15 19:02:57.963: Tnl 47100 L2TP: Congestion Control event received is retransmission
*Jul 15 19:02:57.963: Tnl 47100 L2TP: Congestion Window size, Cwnd 1
*Jul 15 19:02:57.963: Tnl 47100 L2TP: Slow Start threshold, Ssthresh 2
*Jul 15 19:02:57.963: Tnl 47100 L2TP: Remote Window size, 500
*Jul 15 19:02:57.963: Tnl 47100 L2TP: Control channel retransmit delay set to 4 seconds
*Jul 15 19:03:01.607: Tnl 47100 L2TP: Update ns/nr, peer ns/nr 2/5, our ns/nr 5/2
The following partial example shows that traffic has been restarted with L2TP congestion avoidance throttling traffic:
Device# debug vpdn l2x-events
.
.
.
*Jul 15 14:45:16.123: Tnl 30597 L2TP: Control channel retransmit delay set to 2 seconds
*Jul 15 14:45:16.123: Tnl 30597 L2TP: Tunnel state change from idle to wait-ctl-reply
*Jul 15 14:45:16.131: Tnl 30597 L2TP: Congestion Control event received is positive acknowledgement
*Jul 15 14:45:16.131: Tnl 30597 L2TP: Congestion Window size, Cwnd 2
*Jul 15 14:45:16.131: Tnl 30597 L2TP: Slow Start threshold, Ssthresh 500
*Jul 15 14:45:16.131: Tnl 30597 L2TP: Remote Window size, 500
*Jul 15 14:45:16.131: Tnl 30597 L2TP: Congestion Ctrl Mode is Slow Start
The table below describes the significant fields shown in the displays. See RFC 2661 for more details about the information
in the reports for L2TP congestion avoidance.
Table 5. debug vpdn l2x-events Field Descriptions—L2TP Congestion Avoidance
Field
|
Description
|
Control channel retransmit delay set to ...
|
Indicates the current value set for the retransmit delay.
|
Tunnel state...
|
Indicates the tunnel’s current Control Connection State, per RFC 2661.
|
Congestion Control event received is...
|
Indicates the received congestion control event.
|
Congestion Window size, Cwnd 2
|
Current size of the Cwnd.
|
Slow Start threshold, Ssthresh 500
|
Current value of the slow start threshold (Ssthresh).
|
Remote Window size, 500
|
Size of the advertised receive window configured on the remote peer with the
l2tp
tunnel
receive-window command.
|
Congestion Ctrl Mode is...
|
Indicates whether the device is operating in Slow Start or Congestion Avoidance mode.
|
Update ns/nr, peer ns/nr 2/5, our ns/nr 5/2
|
See RFC 2661.
|
Examples
The following is sample output from the
debug
vpdn
error command on a NAS when the L2F tunnel is not set up:
Device# debug vpdn error
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async1, changed state to down
%LINK-5-CHANGED: Interface Async1, changed state to reset
%LINK-3-UPDOWN: Interface Async1, changed state to down
%LINK-3-UPDOWN: Interface Async1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async1, changed state to up
VPDN tunnel management packet failed to authenticate
VPDN tunnel management packet failed to authenticate
The table below describes the significant fields shown in the display.
Table 6. debug vpdn error Field Descriptions for the NAS
Field
|
Description
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async1, changed state to down
|
Line protocol on the asynchronous interface went down.
|
%LINK-5-CHANGED: Interface Async1, changed state to reset
|
Asynchronous interface 1 was reset.
|
%LINK-3-UPDOWN: Interface Async1, changed state to down
%LINK-3-UPDOWN: Interface Async1, changed state to up
|
Link from asynchronous interface 1 link went down and then came back up.
|
%LINEPROTO-5-UPDOWN: Line protocol on Interface Async1, changed state to up
|
Line protocol on the asynchronous interface came back up.
|
VPDN tunnel management packet failed to authenticate
|
Tunnel authentication failed. This is the most common VPDN error.
Note
|
Verify the password for the NAS and the tunnel server name.
|
If you store the password on an AAA server, you can use the
debug
aaa
authentication command.
|
The following is sample output from the
debug
vpdn
l2x-errors command:
Device# debug vpdn l2x-errors
%LINK-3-UPDOWN: Interface Async1, changed state to up
L2F Out of sequence packet 0 (expecting 0)
L2F Tunnel authentication succeeded for example.com
L2F Received a close request for a non-existent mid
L2F Out of sequence packet 0 (expecting 0)
L2F packet has bogus1 key 1020868 D248BA0F
L2F packet has bogus1 key 1020868 D248BA0F
The table below describes the significant fields shown in the display.
Table 7. debug vpdn l2x-errors Field Descriptions
Field
|
Description
|
%LINK-3-UPDOWN: Interface Async1, changed state to up
|
The line protocol on the asynchronous interface came up.
|
L2F Out of sequence packet 0 (expecting 0)
|
Packet was expected to be the first in a sequence starting at 0, but an invalid sequence number was received.
|
L2F Tunnel authentication succeeded for example.com
|
Tunnel was established from the NAS to the tunnel server, example.com.
|
L2F Received a close request for a non-existent mid
|
Multiplex ID was not used previously; cannot close the tunnel.
|
L2F Out of sequence packet 0 (expecting 0)
|
Packet was expected to be the first in a sequence starting at 0, but an invalid sequence number was received.
|
L2F packet has bogus1 key 1020868 D248BA0F
|
Value based on the authentication response given to the peer during tunnel creation. This packet, in which the key does not
match the expected value, must be discarded.
|
L2F packet has bogus1 key 1020868 D248BA0F
|
Another packet was received with an invalid key value. The packet must be discarded.
|
Examples
The following is sample output from the
debug
vpdn
l2x-packets command on a NAS. This example displays a trace for a
ping command.
Device# debug vpdn l2x-packets
L2F SENDING (17): D0 1 1 10 0 0 0 4 0 11 0 0 81 94 E1 A0 4
L2F header flags: 53249 version 53249 protocol 1 sequence 16 mid 0 cid 4
length 17 offset 0 key 1701976070
L2F RECEIVED (17): D0 1 1 10 0 0 0 4 0 11 0 0 65 72 18 6 5
L2F SENDING (17): D0 1 1 11 0 0 0 4 0 11 0 0 81 94 E1 A0 4
L2F header flags: 53249 version 53249 protocol 1 sequence 17 mid 0 cid 4
length 17 offset 0 key 1701976070
L2F RECEIVED (17): D0 1 1 11 0 0 0 4 0 11 0 0 65 72 18 6 5
L2F header flags: 57345 version 57345 protocol 2 sequence 0 mid 1 cid 4
length 32 offset 0 key 1701976070
L2F-IN Output to Async1 (16): FF 3 C0 21 9 F 0 C 0 1D 41 AD FF 11 46 87
L2F-OUT (16): FF 3 C0 21 A F 0 C 0 1A C9 BD FF 11 46 87
L2F header flags: 49153 version 49153 protocol 2 sequence 0 mid 1 cid 4
length 32 offset 0 key -2120949344
L2F-OUT (101): 21 45 0 0 64 0 10 0 0 FF 1 B9 85 1 0 0 3 1 0 0 1 8 0 62 B1
0 0 C A8 0 0 0 0 0 11 E E0 AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD
AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB
CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD
L2F header flags: 49153 version 49153 protocol 2 sequence 0 mid 1 cid 4
length 120 offset 3 key -2120949344
L2F header flags: 49153 version 49153 protocol 2 sequence 0 mid 1 cid 4
length 120 offset 3 key 1701976070
L2F-IN Output to Async1 (101): 21 45 0 0 64 0 10 0 0 FF 1 B9 85 1 0 0 1 1 0
0 3 0 0 6A B1 0 0 C A8 0 0 0 0 0 11 E E0 AB CD AB CD AB CD AB CD AB CD AB CD
AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB
CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD AB CD
The table below describes the significant fields shown in the display.
Table 8. debug vpdn l2x-packets Field Descriptions
Field
|
Description
|
L2F SENDING (17)
|
Number of bytes being sent. The first set of “SENDING”...“RECEIVED” lines displays L2F keepalive traffic. The second set
displays L2F management data.
|
L2F header flags:
|
Version and flags, in decimal.
|
version 53249
|
Version number.
|
protocol 1
|
Protocol for negotiation of the point-to-point link between the NAS and the tunnel server is always 1, indicating L2F management.
|
sequence 16
|
Sequence numbers start at 0. Each subsequent packet is sent with the next increment of the sequence number. The sequence
number is thus a free running counter represented modulo 256. There is a distinct sequence counter for each distinct MID value.
|
mid 0
|
MID, which identifies a particular connection within the tunnel. Each new connection is assigned a MID currently unused within
the tunnel.
|
cid 4
|
Client ID used to assist endpoints in demultiplexing tunnels.
|
length 17
|
Size in octets of the entire packet, including header, all fields pre-sent, and payload. Length does not reflect the addition
of the checksum, if present.
|
offset 0
|
Number of bytes past the L2F header at which the payload data is expected to start. If it is 0, the first byte following
the last byte of the L2F header is the first byte of payload data.
|
key 1701976070
|
Value based on the authentication response given to the peer during tunnel creation. During the life of a session, the key
value serves to resist attacks based on spoofing. If a packet is received in which the key does not match the expected value,
the packet must be silently discarded.
|
L2F RECEIVED (17)
|
Number of bytes received.
|
L2F-IN Output to Async1 (16)
|
Payload datagram. The data came in to the VPDN code.
|
L2F-OUT (16):
|
Payload datagram sent out from the VPDN code to the tunnel.
|
L2F-OUT (101)
|
Ping payload datagram. The value 62 in this line is the ping packet size in hexadecimal (98 in decimal). The three lines
that follow this line show ping packet data.
|
Examples
The following example shows output from the
debug
vpdn
l2x-events command for an L2TP version 3 (L2TPv3) xconnect session on an Ethernet interface:
Device# debug vpdn l2x-events
23:31:18: L2X: l2tun session [1669204400], event [client request], old state [open], new state [open]
23:31:18: L2X: L2TP: Received L2TUN message <Connect>
23:31:18: Tnl/Sn58458/28568 L2TP: Session state change from idle to wait-for-tunnel
23:31:18: Tnl/Sn58458/28568 L2TP: Create session
23:31:18: Tnl58458 L2TP: SM State idle
23:31:18: Tnl58458 L2TP: O SCCRQ
23:31:18: Tnl58458 L2TP: Control channel retransmit delay set to 1 seconds
23:31:18: Tnl58458 L2TP: Tunnel state change from idle to wait-ctl-reply
23:31:18: Tnl58458 L2TP: SM State wait-ctl-reply
23:31:18: Tnl58458 L2TP: I SCCRP from router
23:31:18: Tnl58458 L2TP: Tunnel state change from wait-ctl-reply to established
23:31:18: Tnl58458 L2TP: O SCCCN to router tnlid 8012
23:31:18: Tnl58458 L2TP: Control channel retransmit delay set to 1 seconds
23:31:18: Tnl58458 L2TP: SM State established
23:31:18: Tnl/Sn58458/28568 L2TP: O ICRQ to router 8012/0
23:31:18: Tnl/Sn58458/28568 L2TP: Session state change from wait-for-tunnel to wait-reply
23:31:19: Tnl58458 L2TP: Control channel retransmit delay set to 1 seconds
23:31:20: %LINK-3-UPDOWN: Interface Ethernet2/1, changed state to up
23:31:21: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet2/1, changed state to up
23:31:25: L2X: Sending L2TUN message <Connect OK>
23:31:25: Tnl/Sn58458/28568 L2TP: O ICCN to router 8012/35149
23:31:25: Tnl58458 L2TP: Control channel retransmit delay set to 1 seconds
23:31:25: Tnl/Sn58458/28568 L2TP: Session state change from wait-reply to established
23:31:25: L2X: l2tun session [1669204400], event [server response], old state [open], new state [open]
23:31:26: Tnl58458 L2TP: Control channel retransmit delay set to 1 seconds
Examples
The following example shows debug messages for control channel authentication failure events in Cisco IOS Release 12.0(31)S:
Device# debug vpdn l2x-events
Tnl41855 L2TP: Per-Tunnel auth counter, Overall Failed, now 1
Tnl41855 L2TP: Tunnel auth counter, Overall Failed, now 219