Ospf rid

GDaines

I understand the statement "The RID will be the highest active loopback interface on the router, but if non are configured it will be the highest active physical interface", but can someone tell me which of these is deemed to be the 'highest'?


1.1.1.1
10.10.10.10


In sport coming first puts you highest, but numerically 10 is bigger than 1. In all the material I've read or watched so far there never seem to be two loopback interfaces configured, so it's never been clear which would be used for the RID.

Thanks.

squawk1500

Highest number = 1st

GDaines

Thanks.

I've just thought to myself, perhaps I should actually check my new routers and then set up OSPF in my lab, in which case I could have configured two loopback interfaces and seen which one was used for the RID. I've been watching videos all weekend though so even the obvious isn't so obvious just now.

volfkhat

GDaines,
to answer your Q,the RID will look for the highest "numerical" value.

In your example:
1.1.1.1
10.10.10.10
~ Start with the first octet, and compare the values.
"10" is GREATER than "1".
And there you have it.
the RID will select the loopback interface 10.10.10.10

ANother example:
192.168.1.0
192.168.2.0
192.168.3.0

~You follow the same steps.
The first octet (192): TIE.
The second octet (16: TIE.
The third octet: Different.
the RID will select the loopback interface 192.168.3.0

Hope that helps!