OSPF - Router ID

R1(config)#router os 1
R1(config-router)#router-id 1.1.1.1

R1#sh ip protocols

Routing Protocol is "ospf 1"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  Router ID 1.1.1.1 <== [HERE!!]

This is router ID cannot be changed, once some interface has run OSPF.

R1(config-router)#

*Mar  1 00:43:06.031: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial1/0 from LOADING to FULL, Load

R1(config-router)#router-id 2.2.2.2

Reload or use "clear ip ospf process" command, for this to take effect <== [Here]

R1(config-router)#