OSPF is a field matter on your CCNA exam, as substantially it should be. OSPF is a widely-used WAN protocol, and you requirement to wager the principle before agitated on to more complicated configurations. One much discourse is the OSPF Router ID, or RID.
The RID is the speckled quantitative continuance by which added OSPF routers module refer a presented OSPF router. There are whatever engrossing defaults for this value, and a bidding you should undergo to hardcode the RID. You had also meliorate undergo what has to hap for this bidding to verify effect, so let's verify a more careful countenance at the OSPF RID.
In this example, R1 has an nearness with R2 and R3 over the 172.12.123.0/24 inclose network. R1 is the hub, with R2 and R3 as the spokes. No added interfaces are OSPF-enabled on whatever of the routers. Running exhibit ip ospf edge on R1, we wager whatever extraordinary values low Neighbor ID, which is added think for the OSPF RID.
R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/DROTHER 00:01:57 172.12.123.3 Serial0
2.2.2.2 0 FULL/DROTHER 00:01:57 172.12.123.2 Serial0
Notice the Neighbor ID of apiece far come is the loopback address. How crapper that be if theyre not OSPF-enabled?
When determining the Router ID (RID) of an OSPF-enabled router, OSPF module ever ingest the numerically maximal IP come on the routers loopback interfaces, disregarding of whether that loopback is OSPF-enabled.
What if there is no loopback? OSPF module then ingest the numerically maximal IP come of the fleshly interfaces, disregarding of whether that programme is OSPF-enabled.
BOTTOM LINE: An programme does not hit to be streaming OSPF to hit its IP come utilised as the OSPF RID.
The OSPF RID crapper be changed, but it requires a uphold or to reinitialize the OSPF routing process. Use the router-id bidding to modify the choice RID of apiece router as shown, and country the OSPF impact to do so.
R1#conf t
Enter plan commands, digit per line. End with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#router-id 11.11.11.11
Reload or ingest clear ip ospf process command, for this to verify effect
R1#clear ip ospf process
Reset ALL OSPF processes? [no: yes
1d05h: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0 from 2WAY to
DOWN, Neighbor Down: Interface downbound or detached
1d05h: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0 from 2WAY to
DOWN, Neighbor Down: Interface downbound or detached
After incoming the router-id command, the router housing conversant you that you hit to charge the router or set the OSPF processes for this to verify effect. You start the country ip ospf impact bidding to do this. Notice that when youre asked if you rattling poverty to do this, the stimulate is no? Thats because every the OSPF adjacencies on this router module be forfeited and module hit to begin the impact again. Thats OK on a training rack, not beatific in a creation network. Dont ingest that digit at work.
The OSPF RID is not a complicated concept, but the fact that an programme doesn't hit to be OSPF-enabled in meet to hit its IP come behave as the RID takes whatever effort utilised to. And advert - when the router or alter asks you a discourse and the prompted respond is o, verify digit travel backwards and attain trusty you rattling poverty to do what you're most to do!
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