[c-nsp] IS-IS Multiarea on 12.2 SR

[Richard A Steenbergen]

On Mon, Nov 09, 2009 at 02:32:11PM +0800, Mark Tinka wrote:
> On Sunday 08 November 2009 07:33:55 pm Richard A Steenbergen 
> wrote:
> 
> > IMHO the rule of thumb for multiple areas in either ISIS
> > or OSPF is "if you have to ask whether you should use
> > them or not, the answer is you shouldn't". Their sensible
> > use is so vastly exagerated in books and lab tests that
> > it isn't even funny.
> 
> Speaking on my/our own behalf, there wouldn't be a doubt in 
> our minds whether we needed the hierarchy or not.
> 
> In our case, coming from OSPF where Areas were in vast use 
> (different for each PoP, and we had quite a few), it made 
> sense, at the time, to maintain a similar hierarchy in IS-
> IS, especially since what we wanted the most out of the 
> migration was its "stretchy" property.
> 
> However, like I mentioned in an earlier post, it quickly 
> dawned on us that since Route Leaking essentially adds all 
> L1 routes from other PoP's into the L1 database in other 
> PoP's, and you turn off the ATT bit to gain optimality, the 
> point of running both L1 and L2 for scaling reasons quickly 
> becomes moot.

I'm not questioning your decision, I'm just stating it for the archives
and for everyone else who has to make this same decision at some point
in the future: If you have to ask, just don't do it. I see way too many
people trying to deploy areas with 10 router networks because they read
somewhere that it was what they were supposed to do to scale, or because 
people saw it on an exam somewhere.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)