IGP choice

Mark Tinka mark.tinka at seacom.mu
Thu Oct 22 19:58:25 UTC 2015

On 22/Oct/15 21:35, Dave Bell wrote:

> I'm unsure if this is a serious argument, but its such a poor point
> today. Everything has to be connected to a level 2 in IS-IS. If you
> want a flat area 0 network in OSPF, go nuts. As long as you are
> sensible about what you put in your IGP, both IS-IS and OSPF scale
> very well.
> The differences between the two protocols are so small, that people
> really grasp at straws when 'proving' that one is better over the
> other. 'IS-IS doesn't work over IP, so its more secure'. 'IS-IS uses
> TLVs so new features are quicker to implement'. While these may be
> vaguely valid arguments, they don't hold much water. If you don't
> secure your routers to bad actors forming OSPF adjacencies with you,
> you're doing something wrong.Who is running code that is so bleeding
> edge that feature X might be available for IS-IS, but not OSPF?
> Chose whichever you and your operational team are most comfortable
> with, and run with it.

OSPFv3 scaled better than OSPFv2 in 2008. But multi-AF support for
OSPFv3 was only developing then, so that was not a viable replacement
for OSPFv2.

OSPFv2 should scale better in 2015 (I say "should" because more routers
now have x86-based control planes, but I don't run OSPF so I'm hand-waving).

You're right, a single Level-2 domain in IS-IS is akin to a single Area
0 in OSPF. But those "so small" differences between the protocols in
2008 meant I was less eager to try the single area with OSPF than I was
the single level with IS-IS.


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