Configure OSPF Graceful Restart

OSPF Graceful Restart directs OSPF neighbors to continue using routes through a firewall during a short transition when it is out of service. This behavior increases network stability by reducing the frequency of routing table reconfiguration and the related route flapping that can occur during short periodic down times.
For a Palo Alto Networks
firewall, OSPF Graceful Restart involves the following operations:
  • Firewall as a restarting device
    —If the firewall will be down for a short period of time or is unavailable for short intervals, it sends Grace LSAs to its OSPF neighbors. The neighbors must be configured to run in Graceful Restart helper mode. In helper mode, the neighbor receives Grace LSAs informing it that the firewall will perform a graceful restart within a specified period of time defined as the
    Grace Period
    . During the grace period, the neighbor continues to forward routes through the firewall and to send LSAs that announce routes through the firewall. If the firewall resumes operation before expiration of the grace period, traffic forwarding will continue as before without network disruption. If the firewall does not resume operation after the grace period has expired, the neighbors will exit helper mode and resume normal operation, which will involve reconfiguring the routing table to bypass the firewall.
  • Firewall as a Graceful Restart Helper
    —If neighboring routers may be down for short periods of time, the firewall can be configured to operate in Graceful Restart helper mode, in which case the firewall employs a
    Max Neighbor Restart Time
    . When the firewall receives the Grace LSAs from its OSPF neighbor, it continues to route traffic to the neighbor and advertise routes through the neighbor until either the grace period or max neighbor restart time expires. If neither expires before the neighbor returns to service, traffic forwarding continues as before without network disruption. If either period expires before the neighbor returns to service, the firewall exits helper mode and resumes normal operation, which involves reconfiguring the routing table to bypass the neighbor.
  1. Select
    Virtual Routers
    and select the virtual router you want to configure.
  2. Select
  3. Verify that the following are selected (they are enabled by default):
    • Enable Graceful Restart
    • Enable Helper Mode
    • Enable Strict LSA Checking
    These should remain selected unless required by your topology.
  4. Configure a
    Grace Period
    in seconds.
  5. Configure a
    Max Neighbor Restart Time
    in seconds.

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