ROUTER ID ELECTION IN OSPF

[pardeep.sharma8681]

I have one router configured with ospf int fa0/0 172.16.1.1 255.255.255.0 and another int fa0/1 configured with eigrp 10 with 192.168.1.1 255.255.255.0. which will be router id in ospf domain. 

[Ganesh Hariharan]

Hello Pradeep,

A RID is the highest logical (loopback) IP address configured on a router, if no logical/loopback IP address is set then the Router uses the highest IP address configured on its active interfaces.

Hope it Helps..

-GI

[InayathUlla Sharieff]

OSPF Router ID selection algorithm works as below.

• Any manually configured OSPF Router ID in OSPF Process is selected as the OSPF Router ID.

• If there is no OSPF Router ID configured, the highest IP address on any of the Routers Loopback Interfaces is selected as the OSPF Router ID.

• If there is no Loopback Interfaces configured, the highest IP address on its active interfaces is selected as the OSPF Router ID.

In your case the ip address 192.168.1.1 will be selected as router id.

HTH

[Kevin Dorrell]

Personally, I always set the router-id manually.  You know where you stand that way.  In fact, if you set the router id manually it does not need to be related to any IP address at all - it is just an arbitrary 32-bit number.  Relating the router-id to an IP address on the router is just a convenient way to generate that arbitrary 32-bit number and to guarantee that it is unique.

Kevin

[Mark Malone]

Hey to add to the points below you need to remember what there used for EIGRP rid is used for preventing external routing loops in the protocol while OSPF rid is used to make it unique in the LSDB database so both have there values specific to there protocol

If these subnets are specific to each protocol then they can only be the rid for that protocol its not explicitly for the router itself in hardware but more for the protocol they belong too so the 192.168.1.1 should not be the rid for OSPF as OSPF should know nothing about it unless you have advertised that in OSPF as well which is unlikely as already advertised in EIGRP

[Masoud Pourshabanian]

hello,

192.168.1.1 will be the router ID. OSPF chooses the highest IP regardless of that IP being in OSPF domain or not. Here is the algorithm which has been mention by others.

1- Router ID configured under OSPF

2-Highest IP of loopback interface.

3-Highest IP of physical interface if no loopback presents.

Hope it helps,

Masoud