On 10/Nov/16 04:45, RT Parrish wrote:
> 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. L2 IS-IS can be as chatty as single-area OSPF. That said, IS-IS has native tools to reduce that chatter (like PRC, and iSPF), but to be honest, I'm not sure it makes much of a difference given today's faster router CPU's. > 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. I've noticed that the delay between when IS-IS and/or OSPF pick up a feature the other already has is reasonable. By the time an OSPF has completed evaluating whether they need LFA, it would have been implemented in the IGP. I suppose back then, there was a much bigger between when features made it between both protocols, but things seem to be on par nowadays. > 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. OSPFv3 can support the advertisement of IPv4 prefixes. But you'd still need an IPv6 link layer. > 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. Agree. > > End of the day, use the right tool/vendor/technology for the right job. Agree. Mark.
