OSPF router ID change issue

[olly ahmed]

Can anyone help me regarding the OSPF

router-id

change issue. I made up a new interface with higher ip address by no shut command and then applied

clear ip ospf (pid) process

but it does not show the new higher IP address as

router-id

For better understanding below is the situation :

At the start of OSPF process:

R3#sh
R3#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 2.2.2.2 YES NVRAM up up
FastEthernet1/0 5.5.5.5 YES NVRAM up up
FastEthernet1/1 10.10.10.10 YES NVRAM administratively down down
GigabitEthernet2/0 unassigned YES NVRAM administratively down down
R3#

R3#show ip ospf
 Routing Process "ospf 1" with ID 5.5.5.5
Start time: 00:00:04.952, Time elapsed: 00:00:08.500

After I make the interface 1/1 with highest ip address by no shut and clear ip ospf 1 process

R3(config)#interface fa1/1
R3(config-if)#no shut

*Jun 25 15:15:15.031: %LINK-3-UPDOWN: Interface FastEthernet1/1, changed state to up

R3(config-if)#

*Jun 25 15:15:16.031: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/1, changed state to up

R3#clear ip ospf 1 process
Reset OSPF process? [no]: yes
R3#
*Jun 25 15:15:30.611: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.1 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Jun 25 15:15:30.803: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.1 on FastEthernet0/0 from LOADING to FULL, Loading Done

R3#sh ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 2.2.2.2 YES NVRAM up up
FastEthernet1/0 5.5.5.5 YES NVRAM up up
FastEthernet1/1 10.10.10.10 YES NVRAM up up
GigabitEthernet2/0 unassigned YES NVRAM administratively down down
R3#


R3#show ip ospf
 Routing Process "ospf 1" with ID 5.5.5.5
Start time: 00:00:04.952, Time elapsed: 00:04:40.744

Please let me know if you know further clarification.

[Peter Paluch · Accepted solution]

Hello,

According to my experience, once the RID of an OSPF process has been chosen, it will not change on its own, not even if you restart the OSPF process.

Specifically, in your case, the RID of an OSPF process will not change if a new interface is added that happens to have a higher IP address than the RID. Not even clearing the OSPF process will cause it to change its RID.

To force an OSPF process to change its RID, you have to use the

router-id

command in its configuration, followed by

clear ip ospf process

command. If you then remove the

router-id 

command and restart the OSPF process once again, it will elect its RID from the existing interfaces according to the usual rules.

So the behavior you have experienced is correct. You have to force OSPF manually into using a different RID; merely restarting the process is not enough.

Best regards,
Peter