Concept Guide

• Helper-only: the OSPFv2 router supports graceful-restart only as a helper router.
• Restart-only: the OSPFv2 router supports graceful-restart only during unplanned restarts.
By default, OSPFv2 supports both restarting and helper roles. Selecting one or the other role restricts OSPFv2 to the single selected
role.
To disable OSPFv2 graceful-restart after you have enabled it, use the no graceful-restart grace-period command in CONFIG-
ROUTEROSPF- id mode. The command returns OSPF graceful-restart to its default state.
NOTE: The Helper mode is enabled by default on the device. To enable the restart mode also on the device, you must congure
the grace period using the graceful-restart grace-period command. After you enable restart mode the router
advertises the neighbor as fully adjacent during a restart.
For more information about OSPF graceful restart, refer to the Dell EMC Networking OS Command Line Reference Guide.
Example of the show run ospf Command
When you congure a graceful restart on an OSPFv2 router, the show run ospf command displays information similar to the following.
DellEMC#show run ospf
!
router ospf 1
graceful-restart grace-period 300
graceful-restart role helper-only
graceful-restart mode unplanned-only
graceful-restart helper-reject 10.1.1.1
graceful-restart helper-reject 20.1.1.1
network 10.0.2.0/24 area 0
DellEMC#
Creating Filter Routes
To lter routes, use prex lists. OSPF applies prex lists to incoming or outgoing routes.
Incoming routes must meet the conditions of the prex lists. If they do not, OSPF does not add the route to the routing table. Congure
the prex list in CONFIGURATION PREFIX LIST mode prior to assigning it to the OSPF process.
• Create a prex list and assign it a unique name.
CONFIGURATION mode
ip prefix-list prefix-name
You are in PREFIX LIST mode.
• Create a prex list with a sequence number and a deny or permit action.
CONFIG- PREFIX LIST mode
seq sequence-number {deny |permit} ip-prefix [ge min-prefix-length] [le max-prefix-length]
The optional parameters are:
– ge min-prefix-length: is the minimum prex length to match (from 0 to 32).
– le max-prefix-length: is the maximum prex length to match (from 0 to 32).
For conguration information about prex lists, refer to Access Control Lists (ACLs).
Applying Prex Lists
To apply prex lists to incoming or outgoing OSPF routes, use the following commands.
• Apply a congured prex list to incoming OSPF routes.
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Open Shortest Path First (OSPFv2 and OSPFv3)