Timer and Retry Enhancements for L2TP and L2F
Available Languages
Table Of Contents
Timer and Retry Enhancements for L2TP and L2F
l2f tunnel retransmit initial retries
l2tp tunnel retransmit initial retries
l2tp tunnel retransmit initial timeout
Timer and Retry Enhancements for L2TP and L2F
The Timer and Retry Enhancements for L2TP and L2F feature introduces configurable control packet timers and retry counters for Layer 2 Transport Protocol (L2TP) and Layer 2 Forwarding (L2F) virtual private dialup network (VPDN) tunnels. Adjustments to these timers and counters allows you to configure the following parameters:
•
The amount of time that a router will wait for a reply while establishing a VPDN tunnel.
•
•
These customizable timers and counters allow fine-tuning of router performance to suit the particular needs of the VPDN deployment.
Configuration Information
Configuration information is included in the "VPDN Tunnel Management" module in the Cisco IOS VPDN Configuration Guide, Release 12.4T, at the following URL:
•
Command Reference
This section documents modified commands.
•
•
•
•
l2f tunnel busy timeout
To configure the amount of time that the router will wait before attempting to recontact a Layer 2 Forwarding (L2F) peer that was previously busy, use the l2f tunnel busy timeout command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2f tunnel busy timeout seconds
no l2f tunnel busy timeout
Syntax Description
seconds
Time, in seconds, to wait before checking for router availability. This value can range from 60 to 6000. The default value is 300.
Command Default
The router will wait 300 seconds before attempting to recontact a previously busy peer.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Examples
The following example configures the router to leave an L2F peer on the busy list for 90 seconds. This configuration affects only tunnels associated with the virtual private dialup network (VPDN) group named group1.
vpdn-group group1l2f tunnel busy timeout 90Related Commands
l2f tunnel retransmit initial retries
To configure the number of times that the router will attempt to send the initial control packet for tunnel establishment before considering a Layer 2 Forwarding (L2F) peer busy, use the l2f tunnel retransmit initial retries command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2f tunnel retransmit initial retries number
no l2f tunnel retransmit initial retries
Syntax Description
number
The number of retries that will be attempted, ranging from 1 to 1000. The default value is 2.
Command Default
The router will send the initial control packet twice.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Usage Guidelines
This command can be used only if load sharing is enabled.
Examples
The following example configures a dial-in VPDN group on a network access server (NAS) to load balance calls between two tunnel servers, and to attempt to send the initial L2F control packet five times:
vpdn-group 1request-dialinprotocol l2fdomain cisco.com!initiate-to ip 172.16.0.1 priority 1initiate-to ip 172.16.1.1 priority 2l2f tunnel retransmit initial retries 5Related Commands
l2f tunnel retransmit retries
To configure the number of times the router will attempt to resend a Layer 2 Forwarding (L2F) tunnel control packet before tearing the tunnel down, use the l2f tunnel retransmit retries command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2f tunnel retransmit retries number
no l2f tunnel retransmit retries
Syntax Description
number
The number of retries that will be attempted, ranging from 5 to 1000. The default value is 6.
Command Default
The router will resend control packets six times.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Usage Guidelines
This command does not affect the initial tunnel setup message or session control packets.
Examples
The following example configures the router to resend L2F tunnel control packets ten times before tearing the tunnel down. This configuration affects only tunnels associated with the virtual private dialup network (VPDN) group named group1.
vpdn-group group1l2f tunnel retransmit retries 10Related Commands
l2f tunnel timeout setup
To configure the amount of time that the router will wait for a confirmation message after sending out the initial Layer 2 Forwarding (L2F) control packet before considering a peer busy, use the l2f tunnel timeout setup command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2f tunnel timeout setup seconds
no l2f tunnel timeout setup
Syntax Description
seconds
Time, in seconds, that the router will wait for a return message. This value can range from 5 to 6000. The default value is 10.
Command Default
The router will wait 10 seconds for a confirmation message.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Usage Guidelines
If the router has not received a confirmation message from the peer device before the tunnel timeout setup timer expires, the peer will be placed on the busy list.
Examples
The following example configures a router to wait 25 seconds for confirmation that the initial L2F control packet was received by the peer. This configuration will affect only tunnels associated with the virtual private dialup network (VPDN) group named group1.
vpdn-group group1l2f tunnel timeout setup 25Related Commands
l2tp tunnel busy timeout
To configure the amount of time that the router will wait before attempting to recontact a Layer 2 Transport Protocol (L2TP) peer that was previously busy, use the l2tp tunnel busy timeout command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2tp tunnel busy timeout seconds
no l2tp tunnel busy timeout
Syntax Description
seconds
Time, in seconds, to wait before checking for router availability. This value can range from 60 to 6000. The default value is 300.
Command Default
The router will wait 300 seconds before attempting to recontact a previously busy peer.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Examples
The following example configures tunnels associated with the virtual private dialup network (VPDN) group named group1 to leave an L2TP destination router on the busy list for 90 seconds:
vpdn-group group1l2tp tunnel busy timeout 90Related Commands
l2tp tunnel retransmit initial retries
To configure the number of times that the router will attempt to send out the initial Layer 2 Tunnel Protocol (L2TP) control packet for tunnel establishment before considering a peer busy, use the l2tp tunnel retransmit initial retries command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2tp tunnel retransmit initial retries number
no l2tp tunnel retransmit initial retries
Syntax Description
number
Number of retransmission attempts. Valid values range from 1 to 1000. The default value is 2.
Command Default
The router will resend the initial L2TP control packet twice.
Command Modes
VPDN group configuration
VPDN template configurationCommand History
Usage Guidelines
Use the l2tp tunnel retransmist initial retries command to configure the number of times a device will attempt to resend the initial control packet used to establish an L2TP tunnel.
Examples
The following example configures the router to attempt to send the initial L2TP control packet five times for tunnels associated with the virtual private dialup network (VPDN) group named group1:
vpdn-group group1l2tp tunnel retransmit initial retries 5Related Commands
l2tp tunnel retransmit initial timeout
To configure the amount of time that the router will wait before resending an initial Layer 2 Tunnel Protocol (L2TP) control packet out to establish a tunnel, use the l2tp tunnel retransmit initial timeout command in VPDN group or VPDN template configuration mode. To restore the default value, use the no form of this command.
l2tp tunnel retransmit initial timeout {min | max} seconds
no l2tp tunnel retransmit initial timeout {min | max}
Syntax Description
Command Default
The minimum timeout is one second.
The maximum timeout is eight seconds.Command Modes
VPDN group configuration
VPDN template configurationCommand History
Usage Guidelines
This command will take effect only when load balancing is enabled.
Control channel retransmissions follow an exponential backoff, starting at the minimum retransmit timeout length specified by the min seconds keyword and argument combination. After each packet that is not acknowledged, the timeout exponentially increases until it reaches the value specified by the max seconds keyword and argument combination. For example, if the minimum timeout length is set to one second, the next retransmission attempt occurs two seconds later. The following attempt occurs four seconds later, and all additional attempts occur in eight second intervals.
Examples
The following example configures a network access server (NAS) virtual private dialup network (VPDN) group to establish L2TP tunnels that are load balanced across two tunnel servers. The NAS is configured to attempt to recontact a peer with an initial control packet five times before considering it busy. The timers are set so that the first attempt to recontact the peer will occur two seconds after the initial failure, and the final attempt will occur seven seconds after the previous failure.
vpdn-group 1request-dialinprotocol l2tpdomain cisco.com!initiate-to ip 172.16.0.1 priority 1initiate-to ip 172.16.1.1 priority 2l2tp tunnel retransmit initial retries 5l2tp tunnel retransmit initial timeout min 2l2tp tunnel retransmit initial timeout max 7Related Commands
Feedback