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

[Beatty Lane-Davis]

I think Mr Montagner stopped elegantly short of saying IS-IS is what real men run in the outback wearing Akubra hats while riding horses and drinking VB, single level, no f’n about.

That said, OSPF works just fine everywhere it’s been deployed.

Great to see you all this week!  I hope those organizing folks make good on those more-often meetings things they talked about.

From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Diogo Montagner
Sent: Friday, September 2, 2016 7:32 AM
To: Paul Wilkins <paulwilkins369 at gmail.com>
Cc: Australian Network Operators Mailing List <ausnog at lists.ausnog.net>
Subject: Re: [AusNOG] OSPF vs ISIS - Which do you prefer & why?

Personal opinion certainly weights in a lot.

I dont fully agree with the points made in the article. I think he missed some technical points in his comments.

About this topic, a good reading is Jeff Doyle's book: https://www.amazon.com/OSPF-Choosing-Large-Scale-Networks/dp/0321168798

These days, if you use MPLS as infrastructure of transport, you can easily pick either one.

In terms of resources, as the article pointed out, both rely on SPF algorithm. Hence, what dictates how resource hungry they will be is your network design.

I personally prefer ISIS over OSPF because of the following:

- easier to use, configure and operate in a dual-stack environment, especially if you use MPLS TE.

- the TLV mechanism make it a very flexible routing protocol. Although this point can be argued against (how many protocol changes have we seen till today ?), we don't know what changes might come into this area. I rather prefer to deal with SW upgrades to support new TLVs than replacing an entire IGP for another existing or new one.

On item #1 above, you can easily avoid that if you use MPLS.

One advantage I see on OSPF is its DR/BDR design compared to DIS.

At the end, what really matters is the network design. Both OSPF and ISIS will fit well in a good network design. One or another may save you some headches in a poor network design. But that may not last long .....

My 2c.

Thanks

On Thursday, 1 September 2016, Paul Wilkins <paulwilkins369 at gmail.com<mailto:paulwilkins369 at gmail.com>> wrote:
All I can say is that redistribution between IGPs is never the right answer. OSPF works and is generally well understood.
Kind regards
Paul Wilkins

On 1 September 2016 at 22:25, Michael Bullut <main at kipsang.com<javascript:_e(%7B%7D,'cvml','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.
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