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From: Scott Morris <swm () emanon com>
Date: Fri, 12 Aug 2011 08:56:49 -0400

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The learning curve isn't that big IMHO.  However, it's all about comfort.

You should never design a network because "someone else does it this
way".  While you can certainly take ideas into account about the WHY
their network looks that way, you need to look at your own needs and
desires to figure out if they line up.

If everyone in your organization knows OSPF.  Why force the change?   if
you can't come up with a good reason, then that's a great reason not to
do it, unless there is something missing from OSPF that you need.

The funny thing is that most people learn ISIS in conjunction with what
you already know (OSPF) and what the similarities/differences are in
terms of thinking.

Look at your current design.  I'll assume that you have a reason for the
aspects of your network design that you currently have (as opposed to
someone else did it this way!).  What are they?  How will they translate
to ISIS?  Will they translate?  Do you care?

THAT kind of thing makes a good design for your company.




On 8/12/11 8:23 AM, CJ wrote:
You guys are making a lot of good points.

I will check into the Doyle book to formulate an opinion. So, I am
completely new to the SP environment and OSPF is what I have learned
I have ever only had experience in the enterprise.

It seems that from this discussion, IS-IS is still a real, very viable
option. So, IS-IS being preferred...realistically, what is the learning


On Fri, Aug 12, 2011 at 7:57 AM, jim deleskie <deleskie () gmail com> wrote:

If a network is big enough big / complex enough that you really need
to worry about performance of mesh groups or tweaking areas then its
big enough that having a noc eng page you out at 2am when there is an
issue doesn't really scale. I'm all for ISIS, if I was to build a
network from scratch I'd likely default to it. I'm just say, new
features or performance aside the knowledge of your team under you
will have much more impact on how your network runs then probably any
other factor. I've seen this time and time again when 'new tech' has
been introduced into networks, from vendors to protocols. Most every
time with engineers saying we have smart people they will learn it /
adjust. Almost every case of that turned into 6 mts of crap for both
ops and eng while the ops guys became clueful in the new tech, but as
a friend frequently says Your network, your choice.


On Thu, Aug 11, 2011 at 7:12 PM, Jeffrey S. Young <young () jsyoung net>

On 12/08/2011, at 12:08 AM, CJ <cjinfantino () gmail com> wrote:

Awesome, I was thinking the same thing. Most experience is OSPF so it
makes sense.

That is a good tip about OSPFv3 too. I will have to look more deeply



On Thu, Aug 11, 2011 at 9:34 AM, jim deleskie <deleskie () gmail com>
Having run both on some good sized networks, I can tell you to run
what your ops folks know best. We can debate all day the technical
merits of one v another, but end of day, it always comes down to your
most jr ops eng having to make a change at 2 am, you need to design
for this case, if your using OSPF today and they know OSPF I'd say
stick with it to reduce the chance of things blowing up at 2am when
someone tries to 'fix' something else.


On Thu, Aug 11, 2011 at 10:29 AM, William Cooper <wcooper02 () gmail com>
I'm totally in concurrence with Stephan's point.

Couple of things to consider: a) deciding to migrate to either ISIS or
OSPFv3 from another protocol is still migrating to a new protocol
and b) even in the case of migrating to OSPFv3, there are fairly
significant changes in behavior from OSPFv2 to be aware of (most
authentication, but that's fodder for another conversation).

This topic is a 'once a month' on NANOG, I'm sure we could check
the archives for some point-in-time research but I'm curious to learn
if anyone maintains statistics?

It would be interesting to see statistics on how many service providers
either protocol. IS-IS has, for some years, been the de facto choice for
and as a result the vendor and standardisation community 'used to'
SP features more often for IS-IS. IS-IS was, therefore, more 'mature'
than OSPF
for SP's. I wonder if this is still the case?

For me, designing an IGP with IS-IS is much easier than it is with OSPF.
Mesh groups are far easier to plan (more straightforward) easier to
than OSPF areas. As for junior noc staff touching much of anything to do
with an ISP's IGP at 2am, wake me up instead.


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