OSPF vs IS-IS vs PrivateAS eBGP

Fouant, Stefan Stefan.Fouant at neustar.biz
Sat Sep 12 01:37:07 UTC 2009

I can tell you one reason IS-IS has been traditionally preferred over OSPFv2 is due to it's use of TLVs, which makes IS-IS highly extensible and easy to support new features.  I remember when we first rolled out MPLS code on our core routers at UUnet, support for traffic engineering extensions made it into IS-IS long before OSPFv2 due to the ease with which the developers could augment the protocol.  Opaque LSAs in OSPF have made this situation a bit more bearable, but other things like OSPFv2s tight integration and reliance on IPv4 addressing for proper operation cause other issues, therefore support for things like IPv6 requires an updated protocol - OSPFv3.  If you are running IPv4 and IPv6 in your network you'll need to run both OSPFv2 and OSPFv3.  IS-IS on the other hand, since it is CLNS based and not coupled with IPv4 for transport can support IPv4, IPv6, and whatever new protocol we'll be using whenever we run out of the trillions of IP space that IPv6 will provide.

Sorry for the typos and the top-posting, as I'm on my crackberry.

Stefan Fouant 
Neustar, Inc. / Principal Engineer
46000 Center Oak Plaza Sterling, VA 20166
Office: +1.571.434.5656 ▫ Mobile: + ▫ GPG ID: 0xB5E3803D ▫ stefan.fouant at neustar.biz

----- Original Message -----
From: Glen Kent <glen.kent at gmail.com>
To: Randy Bush <randy at psg.com>
Cc: nanog at nanog.org <nanog at nanog.org>
Sent: Fri Sep 11 20:35:27 2009
Subject: Re: OSPF vs IS-IS vs PrivateAS eBGP

I seem to get the impression that isis is preferred in the core. Any
reasons why folks dont prefer to go with ospf?


On Thu, Aug 20, 2009 at 3:36 PM, Randy Bush <randy at psg.com> wrote:
>> Unless you want your customers to have very substantial control over
>> your  internal network, don't use an SPF IGP like ospf or is-is.
>                                              with your customer ^
> i know that's what you meant, but i thought it worth making it very
> explicit.
> practice safe routing, do not share blood with customer.
> is-is in core with ibgp, and well-filtered ebgp (and packet filters a la
> bcp 38) to customers.
> randy

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