OSPF router id

The study guide states that a router whose id is the loopback address can only be changed by reloading the router where as if the router id is manually entered by router-id command under the ospf process, it can be changed by "clear ip ospf process".

I have found out in my lab that even if the router is using the loopback as the router id, it can also be changed by using "clear ip ospf process".

Anybody geting different results from this, i tried it on IOS 12.4.

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Comments

GT-Rob

I don't know about older versions, but you can change it anytime and just run clear ip ospf pro and the neighbors will see the new one. Whether it be from the router-id command, loopback, or interface IP.

Maybe some older version was different.

singh8281

That is what I figured, Thanks, GT-Rob

Georgecooldude

singh8281 wrote:

The study guide states that a router whose id is the loopback address can only be changed by reloading the router where as if the router id is manually entered by router-id command under the ospf process, it can be changed by "clear ip ospf process".

I have found out in my lab that even if the router is using the loopback as the router id, it can also be changed by using "clear ip ospf process".

Anybody geting different results from this, i tried it on IOS 12.4.

I get the exact opposite results.

Anything derived from the router-id command on the interface is updated with a clear ip ospf process.

Anything derived from a loopback/physical interface upon configuring a new interface and clearing the ip ospf process the RID stays the same. In this instance a reload is required or removing and re-configuring the ospf process.

The CCIE command and configuration hand book says what you say but the BSCI books say what I say. I tested on 12.4 using Cisco 1721 routers.

Plazma

OSPF is kinda wonky sometimes and if you change the router-id it *SHOULD* take affect immediately but doesn't always.

I think if you set the router ID and want ti to become a DR/BDR , and the election has already been held, you have to clear ip ospf process to clear the process and allow the neighborships to form again.