OSPF vs ISIS - Which do you prefer & why?

Thu Nov 10 02:52:42 UTC 2016

Vendor support for IS-IS is quite limited - many options for OSPF.

On Nov 9, 2016 8:47 PM, "RT Parrish" <routetarget at gmail.com> wrote:

> I will definitely be looking up the notes from AOL that John referenced.
> But working for a vendor and getting insight from multiple ISPs, here are a
> few of the things that I hear most frequently:
>
> 1) Network Topology support - The differences between a single OSPF
> backbone area and a contiguous set of Level-2 adjacencies will occasionally
> be a deciding factor.
> 2) Feature Support on a per vendor basis - Some vendors will roll new
> features out in one or the other protocols prior to the other.  Segment
> Routing and some of its enhancements come to mind as being in ISIS first.
> 3) Layer 2 adjacencies - I think someone already mentioned that you form
> adjacencies at layer 2 which also means that with a single adj you can
> support multiple protocols (v4/v6). OSPF would require two different
> instances to support both. Maybe good, maybe not. Depends on your desired
> level of isolation between the two.
> 4) CPU performance is academic at this point - The SPF calculations in most
> networks would require next to no difference between the two protocols even
> if running both IPv4 and v6.
>
> End of the day, use the right tool/vendor/technology for the right job.
>
> Hope this helps,
> RT
>
> On Wed, Nov 9, 2016 at 12:12 PM, Michael Bullut <main at kipsang.com> 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?
> >
> > Warm regards,
> >
> > Michael Bullut.
> >
> > ---
> >
> > *Cell:*
> > *+254 723 393 114.**Skype Name:* *Michael Bullut.*
> > *Twitter:*
> > * @Kipsang <http://twitter.com/Kipsang/>*
> > *Blog: http://www.kipsang.com/ <http://www.kipsang.com/>*
> > *E-mail:* *main at kipsang.com <main at kipsang.com>*
> >
> > *---*
> >
>