Configuring Peer Resynchronization

The JunosE Software enables you to configure the peer resynchronization method you want the router to use. Peer resynchronization enables L2TP to recover from a router warm start and to allow an L2TP failed endpoint to resynchronize with its peer non-failed endpoint.

L2TP peer resynchronization:

To ensure successful peer resynchronization between endpoints, the non-failed endpoint must support a complete RFC-compliant L2TP implementation.

JunosE Software supports both the L2TP silent failover method and the L2TP failover protocol method, which is described in Fail Over extensions for L2TP “failover” draft-ietf-l2tpext-failover-06.txt. You can configure L2TP to use the failover protocol method as the primary peer resynchronization method, but then fall back to the silent failover method if the peer does not support the failover protocol method.

The following list highlights differences between the failover protocol and silent failover peer resynchronization methods:

You can use the CLI or RADIUS to configure the resynchronization method for your router.

  1. Configuring Peer Resynchronization for L2TP Host Profiles and AAA Domain Map Tunnels
  2. Configuring the Global L2TP Peer Resynchronization Method
  3. Using RADIUS to Configure Peer Resynchronization

Configuring Peer Resynchronization for L2TP Host Profiles and AAA Domain Map Tunnels

The JunosE CLI enables you to configure the peer resynchronization method globally, for a host profile, or for a domain map tunnel. A host profile or domain map tunnel configuration takes precedence over the global peer resynchronization configuration.

When you change the peer resynchronization method, the change is not immediately applied to existing tunnels. Tunnels continue using their current resynchronization method until the next time the tunnel is reestablished.

Use the failover-resync command to configure the L2TP peer resynchronization method for L2TP host profiles and AAA domain map tunnels. This command takes precedence over the global peer resynchronization configuration.

Choose one of the following keywords to specify the peer resynchronization method:

By default, peer resynchronization is not configured at the L2TP profile-level or the domain map-level—therefore, the global configuration is used. This is different than using the disable keyword, which specifies that no peer synchronization method is used.

Use the show l2tp destination profile command to display a host profile’s peer resynchronization configuration and the show aaa domain-map command to display a domain map’s configuration.

Configuring the Global L2TP Peer Resynchronization Method

You can configure the peer resynchronization method globally, or for L2TP host profiles or domain map tunnels—a host profile or domain map tunnel configuration takes precedence over the global peer resynchronization configuration.

When you change the peer resynchronization method, the change is not immediately applied to existing tunnels. Tunnels continue using their current resynchronization method until the next time the tunnel is reestablished.

Use the l2tp failover-resync command to configure the global L2TP peer resynchronization method that L2TP failed endpoints use to resynchronize with a peer non-failed endpoint.

Choose one of the following keywords to specify the peer resynchronization method. All tunnels in the chassis use the specified method unless it is overridden by an L2TP host profile configuration or an AAA domain map configuration.

Use the show l2tp command to display the global peer resynchronization configuration.

Using RADIUS to Configure Peer Resynchronization

The JunosE Software supports the use of RADIUS to configure the L2TP peer resynchronization method used by your L2TP tunnels. You use the L2TP-Resynch-Method RADIUS attribute (VSA 26-90) in RADIUS Access-Accept messages to specify the L2TP peer resynchronization method.

Table 78 describes the L2TP-Resynch-Method RADIUS attribute. For more information about RADIUS Access-Accept messages, see Subscriber AAA Access Messages Overview. For more information about the L2TP-Resynch-Method attribute, see RADIUS IETF Attributes.

Table 78: L2TP-Resynch-Method RADIUS Attribute

Standard Number

Attribute Name

Description

Length

Subtype Length

Value

[26-90]

L2TP-Resynch-Method

L2TP peer resynchronization method

12

6

integer:

  • 0 = disabled
  • 1= failover protocol
  • 2 = silent failover
  • 3 = failover protocol with silent failover as backup