North American Network Operators Group

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  • From: Mike Bernico
  • Date: Tue Jun 21 11:05:07 2005

The State of Illinois converted to ISIS in 2002 from EIGRP and it has
definitely been a good thing for us.  It's been operationally bullet
proof, and simple to maintain.  

We typically get features faster than we would if we ran OSPF.  For
example, we have a desire in the future to use IPFRR.  Every indication
from the vendor is that this feature will be available to ISIS first,
most likely because of either the extensibility of ISIS or more likely
because ISIS is in so many larger providers.  

Mike Bernico

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
vijay gill
Sent: Tuesday, June 21, 2005 9:20 AM
To: Dan Evans
Cc: [email protected]
Subject: Re: OSPF -vs- ISIS

Dan Evans wrote:
> All,
> Can anyone point me to information on what the top N service providers
> are using for their IGP? I'm trying to build a case for switching from
> OSPF to IS-IS. Those on this list who are currently running IS-IS, do
> you find better scalability and stability running IS-IS than OSPF? I
> understand that this question is a lot more complex than a simple yes
> or no since factors like design and routing policy will certainly
> affect the protocols behavior.
> Any insights or experiences that you can share would be most helpful.
> Thanks,
> Daniel Evans
> Alltel Communications

Daniel, in short, we've found ISIS to be slightly easier to maintain and

run, with slightly more peace of mind in terms of securitiy than OSPF. 
Performance and stability wise, no major difference that was noticable.

For more information, see the talk by Dave Katz at

Also, AOL's experience in switching from OSPF to ISIS is covered at
the PDF on that page is actually an older version. The full version I 
used at NANOG is available at