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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: