On 9/Nov/16 19:12, 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? I've given a talk about this a couple of times since 2008. But our reasons are to choosing IS-IS are: * No requirement to home everything back to Area 0 (Virtual Links are evil). * Integrated IPv4/IPv6 protocol support in a single IGP implementation. * Single level (L2) deployment at scale. * Scalable TLV structure vs. Options structure for OSPFv2. OSPFv3 employs a TLV structure, however. * Inherent scaling features, e.g., iSPF, PRC, e.t.c. Some of these may not be available on all vendor implementations. If you're interested in reviewing the talk I gave on this, a lot more details is in there at: http://www.apricot.net/apricot2009/images/lecture_files/isis_deployment.pdf Ultimately, router CPU's are way faster now, and I could see a case for running a single-area OSPFv2. So I'd likely not be religious about forcing you down the IS-IS path. Mark.
