[safnog] OSPF vs ISIS - Which do you prefer & why?

Mark Tinka mark.tinka at seacom.mu
Fri Sep 2 11:24:49 UTC 2016



On 1/Sep/16 14:25, Michael Bullut wrote:

> Greetings Team,
>
> ​While I haven't worked with IS-IS before but the only disadvantage
> I've encountered with OSPF is that it is resource intensive on the
> router it is running on which is why only one instance runs on any PE
> & P device on an ISP network. OSPF is pretty good in handling the core
> network routing while BGP & EGP handle the last-mile routing between
> PE & CE devices. BGP & EGP can run on top of OSPF. I came across this
> *article*
> <https://routingfreak.wordpress.com/2011/03/05/why-providers-still-prefer-is-is-over-ospf-when-designing-large-flat-topologies/>
> when scrolling the web a while back and I still want to find out if am
> the only one who thinks its a matter of choice between the two.
> Although there isn't distinct 1:1 argument, it's good we discuss it
> here and figure out why one prefer one over the other /(consider a
> huge flat network)//./ What say you ladies and gentlemen?

In 2016, it's a matter of choice.

We run IS-IS, in our network, and the reason I've always given for that
as being primary to us is that there is no need to connect everything
back to Area 0, like OSPF.

That said, from a technology perspective, I'd say OSPFv3 is closer to
IS-IS. But given the amount of processing and memory capacity in modern
routers (and the advancement of code implementing these protocols), one
can get away with a single "Area 0" OSPF network, just about fine.

Mark.
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