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Configuring Graceful Restart for VPNs

You can configure graceful restart to enable a router to pass through intermediate convergence states that are hidden from the rest of the network. Graceful restart allows a router whose VPN control plane is undergoing a restart (restarting router) to continue to forward traffic while recovering its state from neighboring routers (helper routers).

The restarting router requests a grace period from the neighbor or peer, which can then cooperate with the restarting router. When a restart event occurs and graceful restart is enabled, the restarting router can still forward traffic during the restart period, and convergence in the network is not disrupted. The helper routers hide the restart event from other devices not directly connected to the restarting router. In other words, the restart is not visible to the rest of the network, and the restarting router is not removed from the network topology.

Without graceful restart, a control plane restart disrupts any VPN services provided by the router. Graceful restart is supported on Layer 2 VPNs, Layer 3 VPNs, virtual-router routing instances, and VPLS.

The graceful restart request occurs only if the following conditions are met:

  • The network topology is stable.

  • The neighbor or peer routers cooperate.

  • The restarting router is not already cooperating with another restart already in progress.

  • The grace period does not expire.

Before you begin:

  • Configure the devices for network communication.

  • Configure the device interfaces.

Graceful restart is disabled by default. To enable VPN graceful restart:

  1. Configure graceful restart globally.

    Note:

    • Graceful restart can be enabled on logical systems. To configure graceful restart globally, include the graceful-restart statement at the [edit logical-systems logical-system-name routing-options] or the [edit logical-systems logical-system-name routing-instances routing-instance-name routing-options] hierarchy levels.

    • To disable graceful restart globally, include the disable statement at the [edit routing-options graceful-restart] hierarchy level.

      For example:

  2. Enable or disable graceful restart on a per-protocol, per-group, or per-neighbor basis, depending on the specific protocol, where the most specific definition is used.

  3. Configure graceful restart for Layer 3 VPNS for all routing and MPLS-related protocols within a routing instance. Because you can configure multi-instance BGP and multi-instance LDP, graceful restart for a carrier-of-carriers scenario is supported.

    Note:

    • To disable graceful restart globally, include the disable statement at the [edit routing-instances routing-instance-name routing-options graceful-restart] hierarchy level.

      For example:

    • To disable graceful restart for individual protocols, include the disable statement at the [edit routing-instances routing-instance-name protocols protocol-name graceful-restart] hierarchy level.

      For example:

  4. Configure the duration of the graceful restart period for the routing instance.

    The restart-duration option sets the period of time that the router waits for a graceful restart to be completed. You can configure a time between 1 through 600 seconds. The default value is 300 seconds. At the end of the configured time period, the router performs a standard restart without recovering its state from the neighboring routers. This disrupts VPN services, but is probably necessary if the router is not functioning normally.

    Note:

    You can include the restart-duration option at either the global or routing instance level.