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Configuring Graceful Restart for QFabric Systems

 

When you configure graceful restart in the QFabric CLI, the QFabric system applies the configuration to the network Node group to participate in graceful restart operations with devices external to the QFabric system. Such configuration preserves routing table state and helps neighboring routing devices to resume routing operations more quickly after a system restart. This also enables the network Node group to resume routing operations rapidly if there is a restart in the QFabric system (such as a software upgrade). As a result, we recommend enabling graceful restart for routing protocols in the QFabric CLI.

Note

The QFabric system also uses graceful restart internally within the fabric to facilitate interfabric resiliency and recovery. This internal feature is enabled by default with no configuration required.

Enabling Graceful Restart

By default, graceful restart is disabled. To enable graceful restart, include the graceful-restart statement at the [edit routing-instance instance-name routing-options] or [edit routing-options] hierarchy level.

For example:

To configure the duration of the graceful restart period, include the restart-duration at the [edit routing-options graceful-restart] hierarchy level.

Note

Helper mode (the ability to assist a neighboring router attempting a graceful restart) is enabled by default when you start the routing platform, even if graceful restart is not enabled. You can disable helper mode on a per-protocol basis.

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

When graceful restart is enabled for all routing protocols at the [edit routing-options graceful-restart] hierarchy level, you can disable graceful restart on a per-protocol basis.

Note

If you configure graceful restart after a BGP or LDP session has been established, the BGP or LDP session restarts and the peers negotiate graceful restart capabilities. Also, the BGP peer routing statistics are reset to zero.

Configuring Graceful Restart Options for BGP

To configure the duration of the BGP graceful restart period, include the restart-time statement at the [edit protocols bgp graceful-restart] hierarchy level. To set the length of time the router waits to receive messages from restarting neighbors before declaring them down, include the stale-routes-time statement at the [edit protocols bgp graceful-restart] hierarchy level.

To disable BGP graceful restart capability for all BGP sessions, include the disable statement at the [edit protocols bgp graceful-restart] hierarchy level.

Note

To set BGP graceful restart properties or disable them for a group, include the desired statements at the [edit protocols bgp group group-name graceful-restart] hierarchy level.

To set BGP graceful restart properties or disable them for a specific neighbor in a group, include the desired statements at the [edit protocols bgp group group-name neighbor ip-address graceful-restart] hierarchy level.

Note

Configuring graceful restart for BGP resets the BGP peer routing statistics to zero. Also, existing BGP sessions restart, and the peers negotiate graceful restart capabilities.

Configuring Graceful Restart Options for OSPF and OSPFv3

To configure the duration of the OSPF/OSPFv3 graceful restart period, include the restart-duration statement at the [edit protocols (ospf | ospf3) graceful-restart] hierarchy level. To specify the length of time for which the router notifies helper routers that it has completed graceful restart, include the notify-duration at the [edit protocols (ospf | ospf3) graceful-restart] hierarchy level. Strict OSPF link-state advertisement (LSA) checking results in the termination of graceful restart by a helping router. To disable strict LSA checking, include the no-strict-lsa-checking statement at the [edit protocols (ospf | ospf3) graceful-restart] hierarchy level.

To disable OSPF/OSPFv3 graceful restart, include the disable statement at the [edit protocols (ospf | ospf3) graceful-restart] hierarchy level.

Starting with Release 11.3, the Junos OS supports both the standard (based on RFC 3623, Graceful OSPF Restart) and the restart signaling-based (as specified in RFC 4811, RFC 4812, and RFC 4813) helper modes for OSPF version 2 graceful restart configurations. Both the standard and restart signaling-based helper modes are enabled by default. To disable the helper mode for OSPF version 2 graceful restart configurations, include the helper-disable <both | restart-signaling | standard> statement at the [edit protocols ospf graceful-restart] hierarchy level. Note that the last committed statement always takes precedence over the previous one.

To reenable the helper mode, delete the helper-disable statement from the configuration by using the delete protocols ospf graceful-restarthelper-disable <restart-signaling | standard | both> command. In this case also, the last executed command takes precedence over the previous ones.

Note

Restart signaling-based helper mode is not supported for OSPFv3 configurations. To disable helper mode for OSPFv3 configurations, include the helper-disable statement at the [edit protocols ospfv3 graceful-restart] hierarchy level.

Tip

You can also track graceful restart events with the traceoptions statement at the [edit protocols (ospf | ospf3)] hierarchy level. For more information, see Tracking Graceful Restart Events.

Note

If you configure BFD and graceful restart for OSPF, graceful restart might not work as expected.

Tracking Graceful Restart Events

To track the progress of a graceful restart event, you can configure graceful restart trace options flags for IS-IS and OSPF/OSPFv3. To configure graceful restart trace options, include the graceful-restart statement at the [edit protocols protocol traceoptions flag] hierarchy level: