We have setup OSPF on router and initial it pick ip address 70.xx.xx.33 but later we remove those IPs and reconfigure for new subnet but still OSPF showing older router ID sometime it's confusing seeing older IP address in Router ID, Is there a way i can tell OSPF re-initialize new ID without reload?

R1#sh ip ospf summary-address

            OSPF Router with ID (70.xx.xx.33) (Process ID 1)


Its Cisco C3850 L3 switch with latest IOS running.


You didn't say what model router you have, but assuming a Cisco router (from the configuration example you have) can use the clear ip ospf process command to clear and reload OSPF on a router.

Check the Cisco Documentation:

clear ip ospf

To clear redistribution based on the OSPF routing process ID, use the clear ip ospf command in privileged EXEC mode.

clear ip ospf [pid] {process | redistribution | counters [neighbor [neighbor-interface] [neighbor-id]]}

Syntax Description - enter image description here

Usage Guidelines

Use the pid option to clear only one OSPF process. If the pid option is not specified, all OSPF processes are cleared.


The following example clears all OSPF processes:

clear ip ospf process
  • After googling many folks saying it won't change with clear ip ospf command. They said you need to manually assign ID. its production so i don't want to play. Does it create any issue in future?
    – Satish
    Aug 1 '16 at 16:06
  • What do you mean manually assign ID?
    – Ron Maupin
    Aug 1 '16 at 16:07
  • using router-id A.B.C.D command in OSPF. Read comments of this post blog.ipspace.net/2007/10/…
    – Satish
    Aug 1 '16 at 16:08
  • You need to clear OSPF on the router where the route originated. All the other routers just repeat what it is telling them. The router-id command just manually assigns the router ID, and it is a best practice to do this and assign it to a Loopback address, otherwise the router-ID could change from time to time, as the router gets reloaded.
    – Ron Maupin
    Aug 1 '16 at 16:11
  • 1
    You could, but then, if you decide to use a loopback address to source other protocols, the OSPF router ID won't match. It's nice to have a single address for everything, and just by looking at a router ID or IP address, you know which router it is.
    – Ron Maupin
    Aug 1 '16 at 20:10

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