Router ID Question

kweevuss

I have had this question bothering me for some time, and I haven't figured out 100% what the answer should be.

Suppose you have two routers, Corp and Router 2, on an ethernet link, with networks attached to those routers, and on the Corp router, the serial 0/0 is going to the ISP.

So it would be

ISP-s0/0--- Corp --fa0/0--- Router 2

Corp has these IPs

s0/0 = 192.168.1.1
fa0/0 172.16.0.1

Router 2:
fa0/0 172.16.0.2

Just assume for this that the LAN networks for the clients on each router have lower IPs than these interfaces. My question is with OSPF configured, and the priorities are at the default and no loopbacks, what would be the Router ID for these routers to find out who wins the election for DR.

My first thought is that I know OSPF elections would not try to elect anything over the s0/0 link because its going to the ISP, but since its the highest IP configured on the router, does it still use that IP for the Router ID?

Thanks!!

keenon

it would use the highest ip address configured on the router, if there are no loopback interfaces it can reference first

srg

192.168.1.1 will be used as RID.