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Configuring Graceful Restart

Follow these steps to configure graceful restart on your device.

Enabling Graceful Restart

Graceful restart is disabled by default. You must configure graceful restart at the [edit routing-options] or [edit routing-instances instance-name routing-options] hierarchy level to enable the feature globally.

For example:

You can, optionally, modify the global settings at the individual protocol level or, as of Junos OS 15.1, at the individual routing instance level.

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.

To disable graceful restart, include the disable statement. You can do this globally for all protocols by including the disable statement at the [edit routing-options] hierarchy level, or you can disable graceful restart for a single protocol by including the disable statement at the [edit protocols protocol graceful-restart] hierarchy level. To configure a time period for complete restart, include the restart-duration statement. You can specify a number between 120 and 900.

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.

When you include the graceful-restart statement at the [edit routing-options] hierarchy level, graceful restart is also enabled for aggregate and static routes.

Configuring Graceful Restart

To enable graceful restart, include the graceful-restart statement at the [edit routing-instance instance-name routing-options] or [edit routing-options] hierarchy level. This enables graceful restart globally for all routing protocols. You can, optionally, modify or supplement the global settings at the individual protocol level.

Note:

When set protocols bgp group group-name allow network is configured to accept dynamic BGP sessions, unconfigured-peer-graceful-restart statement should be configured to avoid traffic drop during graceful restart or graceful Routing Engine switchover.

For example:

Figure 1 shows a standard MPLS VPN network. Routers CE1 and CE2 are customer edge routers, PE1 and PE2 are provider edge routers, and P0 is a provider core router. Several Layer 3 VPNs are configured across this network, as well as one Layer 2 VPN. Interfaces are shown in the diagram and are not included in the configuration example that follows.

Figure 1: Layer 3 VPN Graceful Restart TopologyLayer 3 VPN Graceful Restart Topology

Router CE1

On Router CE1, configure the following protocols on the logical interfaces of t3-3/1/0: OSPF on unit 101, RIP on unit 102, BGP on unit 103, and IS-IS on unit 512. Also configure graceful restart, BGP, IS-IS, OSPF, and RIP on the main instance to be able to connect to the routing instances on Router PE1.

Router PE1

On Router PE1, configure graceful restart in the master instance, along with BGP, OSPF, MPLS, and LDP. Next, configure several protocol-specific instances of graceful restart. By including instances for BGP, OSPF, Layer 2 VPNs, RIP, and static routes, you can observe the wide range of options available when you implement graceful restart. Configure the following protocols in individual instances on the logical interfaces of t3-0/0/0: a static route on unit 100, OSPF on unit 101, RIP on unit 102, BGP on unit 103, and Frame Relay on unit 512 for the Layer 2 VPN instance.

Router P0

On Router P0, configure graceful restart in the main instance, along with OSPF, MPLS, and LDP. This allows the protocols on the PE routers to reach one another.

Router PE2

On Router PE2, configure BGP, OSPF, MPLS, LDP, and graceful restart in the master instance. Configure the following protocols in individual instances on the logical interfaces of t1-0/1/3: a static route on unit 200, OSPF on unit 201, RIP on unit 202, BGP on unit 203, and Frame Relay on unit 612 for the Layer 2 VPN instance. Also configure protocol-specific graceful restart in all routing instances, except the Layer 2 VPN instance.

Router CE2

On Router CE2, complete the Layer 2 and Layer 3 VPN configuration by mirroring the protocols already set on Routers PE2 and CE1. Specifically, configure the following on the logical interfaces of t1-0/0/3: OSPF on unit 201, RIP on unit 202, BGP on unit 203, and IS-IS on unit 612. Finally, configure graceful restart, BGP, IS-IS, OSPF, and RIP on the main instance to be able to connect to the routing instances on Router PE2.

Router PE1 Status Before a Restart

The following example displays neighbor relationships on Router PE1 before a restart happens:

Router PE1 Status During a Restart

Before you can verify that graceful restart is working, you must simulate a router restart. To cause the routing process to refresh and simulate a restart, use the restart routing operational mode command:

The following sample output is captured during the router restart:

Configuring VPN Graceful Restart

Graceful restart allows a router whose VPN control plane is undergoing a restart to continue to forward traffic while recovering its state from neighboring routers. 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.

To implement graceful restart for a Layer 2 VPN or Layer 3 VPN, perform the configuration tasks described in the following sections:

Configuring Graceful Restart Globally

To enable graceful restart, include the graceful-restart statement at the [edit routing-options] hierarchy level. To configure a global duration for the graceful restart period, include the restart-duration statement at the [edit routing-options graceful-restart] hierarchy level.

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

Configuring Graceful Restart for the Routing Instance

For Layer 3 VPNs only, you must also configure graceful restart for all routing and MPLS-related protocols within a routing instance by including the graceful-restart statement at the [edit routing-instances instance-name routing-options] hierarchy level. Because you can configure multi-instance BGP and multi-instance LDP, graceful restart for a carrier-of-carriers scenario is supported. To configure the duration of the graceful restart period for the routing instance, include the restart-duration statement at the [edit routing-instances instance-name routing-options].

You can disable graceful restart for individual protocols with the disable statement at the [edit routing-instances instance-name protocols protocol-name graceful-restart] hierarchy level.

Configuring Logical System Graceful Restart

Graceful restart for a logical system functions much as graceful restart does in the main router. The only difference is the location of the graceful-restart statement.

The following topics describe what to configure to implement graceful restart in a logical system:

Enabling Graceful Restart Globally

To enable graceful restart in a logical system, include the graceful-restart statement at the [edit logical-systems logical-system-name routing-options] hierarchy level. To configure a global duration of the graceful restart period, include the restart-duration statement at the [edit logical-systems logical-system-name routing-options graceful-restart] hierarchy level.

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

Configuring Graceful Restart for a Routing Instance

For Layer 3 VPNs only, you must also configure graceful restart globally for a routing instance inside a logical system. To configure, include the graceful-restart statement at the [edit logical-systems logical-system-name routing-instances instance-name routing-options] hierarchy level. Because you can configure multi-instance BGP and multi-instance LDP, graceful restart for a carrier-of-carriers scenario is supported. To configure the duration of the graceful restart period for the routing instance, include the restart-duration statement at the [edit logical-systems logical-system-name routing-instances instance-name routing-options].

To disable graceful restart for individual protocols with the disable statement at the [edit logical-systems logical-system-name routing-instances instance-name protocols protocol-name graceful-restart] hierarchy level.

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:

Example: Managing Helper Modes for OSPF Graceful Restart

Configuration

Step-by-Step Procedure

Both standard and restart signaling-based helper modes are enabled by default, irrespective of the graceful-restart configuration status on the routing device. Junos OS allows you to disable or enable the helper modes based on your requirements.

To configure the helper mode options for graceful restart:

  1. To enable graceful restart, add the graceful-restart statement at the [edit routing-options] hierarchy level.

    The helper modes, both standard and restart signaling-based, are enabled by default.

  2. To disable one or both of the helper modes, add the helper-disable <both | restart-signaling | standard> statement at the [edit protocols ospf graceful-restart] hierarchy level.

    • To disable both standard and restart signaling-based helper modes:

    • To disable only the restart signaling-based helper mode:

    • To disable only the standard helper mode:

    Note:

    You must commit the configuration before the change takes effect.

    The last committed statement always takes precedence over the previous one.

  3. To enable one or both of the helper modes when the helper modes are disabled, delete the helper-disable <both | restart-signaling | standard> statement from the [edit protocols ospf graceful-restart] hierarchy level.

    • To enable both standard and restart signaling-based helper modes:

    • To enable the restart signaling-based helper mode:

    • To enable the standard helper mode:

    Note:

    You must commit the configuration before the change takes effect.

    The last committed statement always takes precedence over the previous one.

Requirements

M Series or T Series routers running Junos OS Release 11.4 or later and EX Series switches.

Overview

Junos OS Release 11.4 extends OSPF graceful restart support to include restart signaling-based helper mode. Both standard (RFC 3623-based) and restart signaling-based helper modes are enabled by default, irrespective of the graceful-restart configuration status on the routing device.

Junos OS, however, enables you to choose between the helper modes with the helper-disable <standard | restart-signaling | both> statement.

Verification

Confirm that the configuration is working properly.

Verifying OSPF Graceful Restart and Helper Mode Configuration

Purpose

Verify the OSPF graceful restart and helper mode configuration on a router.

Action
  • Enter the run show ospf overview command from configuration mode.

Meaning

The output shows that graceful restart and both of the helper modes are enabled.

Tracing Restart Signaling-Based Helper Mode Events for OSPF Graceful Restart

Junos OS provides a tracing option to log restart signaling-based helper mode events for OSPF graceful restart. To enable tracing for restart signaling-based helper mode events, include the traceoptions flag restart-signaling statement at the [edit protocols ospf] hierarchy level.

To enable tracing for restart signaling-based events:

  1. Create a log file for saving the log.

    where ospf-log is the name of the log file.

  2. Enable tracing for restart signaling-based helper mode events.
  3. Commit the configuration.

The logs are saved to the ospf-log file in the /var/log folder.

Viewing the Log File

To view the restart signaling-based events from the log file, type:

Verifying Graceful Restart Operation

This topic contains the following sections:

Graceful Restart Operational Mode Commands

To verify proper operation of graceful restart, use the following commands:

  • show bgp neighbor (for BGP graceful restart)

  • show log (for IS-IS and OSPF/OSPFv3 graceful restart)

  • show (ospf | ospfv3) overview (for OSPF/OSPFv3 graceful restart)

  • show rsvp neighbor detail (for RSVP graceful restart—helper router)

  • show rsvp version (for RSVP graceful restart—restarting router)

  • show ldp session detail (for LDP graceful restart)

  • show connections (for CCC and TCC graceful restart)

  • show route instance detail (for Layer 3 VPN graceful restart and for any protocols using graceful restart in a routing instance)

  • show route protocol l2vpn (for Layer 2 VPN graceful restart)

For more information about these commands and a description of their output fields, see the CLI Explorer.

Verifying BGP Graceful Restart

To view graceful restart information for BGP sessions, use the show bgp neighbor command:

Verifying IS-IS and OSPF Graceful Restart

To view graceful restart information for IS-IS and OSPF, configure traceoptions (see Tracking Graceful Restart Events).

Here is the output of a traceoptions log from an OSPF restarting router:

Here is the output of a traceoptions log from an OSPF helper router:

Verifying CCC and TCC Graceful Restart

To view graceful restart information for CCC and TCC connections, use the show connections command. The following example assumes four remote interface CCC connections between CE1 and CE2:

Change History Table

Feature support is determined by the platform and release you are using. Use Feature Explorer to determine if a feature is supported on your platform.

Release
Description
15.1
You can, optionally, modify the global settings at the individual protocol level or, as of Junos OS 15.1, at the individual routing instance level.