Preventing Creation of New Destinations, Tunnels, and Sessions

You can configure several L2TP drain operations, which determine how the router creates new L2TP destinations, tunnels, and sessions. You can manage the following features:

1. Preventing Creation of New Destinations, Tunnels, and Sessions on the Router
2. Preventing Creation of New Tunnels and Sessions at a Destination
3. Preventing Creation of New Sessions for a Tunnel
4. Specifying a Drain Timeout for a Disconnected Tunnel

Preventing Creation of New Destinations, Tunnels, and Sessions on the Router

You use the l2tp drain command to prevent the creation of new destinations, tunnels, and sessions on the router.

The l2tp drain command and the l2tp shutdown command both affect the administrative state of L2TP on the router. Although each command has a different effect, the no version of each command is equivalent. Each command’s no version leaves L2TP in the enabled state.

• To prevent the creation of new destinations, tunnels, and sessions:
  host1(config)#l2tp drain

Preventing Creation of New Tunnels and Sessions at a Destination

You use the l2tp drain destination command to prevent the creation of new tunnels and sessions at a specific destination.

The l2tp drain destination command and the l2tp shutdown destination command both affect the administrative state of L2TP for the destination. Although each command has a different effect, the no version of each command is equivalent. Each command’s no version leaves L2TP in the enabled state.

• To prevent the creation of new tunnels and sessions at the specified destination:
  host1(config)#l2tp drain destination ip 172.31.1.98

Preventing Creation of New Sessions for a Tunnel

Use the l2tp drain tunnel command to prevent the creation of new sessions for a tunnel.

The l2tp drain tunnel command and the l2tp shutdown tunnel command both affect the administrative state of L2TP for the tunnel. Although each command has a different effect, the no version of each command is equivalent. Each command’s no version leaves L2TP in the enabled state.

• To prevent the creation of new sessions for a specific tunnel:
  host1(config)#l2tp drain tunnel virtual-router default ip 172.31.1.98 isp.com

Specifying a Drain Timeout for a Disconnected Tunnel

Use the l2tp tunnel short-drain-timeout command to specify the amount of time a disconnected LAC L2TP tunnel waits before restarting after it receives a restart request.

You can specify a drain timeout in the range 0–31 seconds. This feature enables the router to restart tunnels more quickly than the standard 31-second drain time specified by RFC-2661. By default, the router uses a short-drain timeout of 2 seconds.

• To specify the short-drain timeout:
  host1(config)#l2tp tunnel short-drain-timeout 12