OSPF vs IS-IS

Jason Duerstock jason.duerstock at gallaudet.edu
Thu Aug 11 09:19:17 CDT 2011


On Thu, Aug 11, 2011 at 8:57 AM, CJ <cjinfantino at gmail.com> wrote:

> Hey all,
>  Is there any reason to run IS-IS over OSPF in the SP core? Currently, we
> are running IS-IS but we are redesigning our core and now would be a good
> time to switch. I would like to switch to OSPF, mostly because of
> familiarity with OSPF over IS-IS.
>  What does everyone think?
>
> --
> CJ
>
> http://convergingontheedge.com <http://www.convergingontheedge.com>
>

Granted, we're not a service provider, so we operate on a different scale
here, but one interesting trick that can be done with ISIS (at least on
Cisco) is this:

router a
-----------
router isis
advertise passive-only

interface loopback0
ip address 10.1.1.1 255.255.255.255

interface vlan2
ip unnumbered loopback0
ip router isis
isis network point-to-point


router b
-----------
(copy router isis definition from router a)

interface loopback0
ip address 10.1.1.2 255.255.255.255

(copy vlan2 definition from router a)

-----------

This removes the associated headaches with /30s or /31s in having to keep
track of their allocation, as well as having them clog the your routing
table.

-waits for replies stating why this is a bad idea-

Now, if I could just get isis-per-vrf-instance support on the Catalyst 6500.

Jason



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