Glen, Yes, if you are referring to RFC5838 like functionality in OSPFv3 (AF support) that is correct. I personally don't have experience with that mode of operation (as the networks I had experience with went dual stack a while back).
I guess someone looking to dual stack now may want to consider that option. I am personally biased towards IS-IS when looking to do both, but to each their own. To further my early points (not saying it's a good option, but adding some context). The rationale for keeping OSPFv2 was due to legacy tools and operational procedures. Adding a second IGP (years ago) for IPv6 was considered (to some) a way of not specifically impacting the "bread and butter" IPv4 service while turning up IPv6. I guess all of that reasoning has likely changed for new IPv6 turn-ups as there is much more operational experience with running multiple AFs now. I should have highlighted the context before sorry. Regards, Victor K From: Glen Kent <[email protected]> Date: Mon, 13 May 2013 00:13:38 +0530 To: Victor Kuarsingh <[email protected]> Cc: "[email protected]" <[email protected]> Subject: Re: ISIS and OSPF together Victor, Folks could, at least theoretically, use ISIS or OSPF multi instance/multi topology extensions to support IPv4 and IPv6 topologies. This way they would only need to run a single protocol and thereby requiring expertise in handling only one protocol. With whatever i remember, OSPFv3 can be used to support IPv4 as well - so folks could also use OSPFv3 when they want to support both IPv4 and IPv6. Glen On Sun, May 12, 2013 at 6:17 PM, Victor Kuarsingh <[email protected]> wrote: > Glen, > > One transition scenario you noted below is often a use case. I have seen > networks move from OSPF to IS-IS (more cases then the reverse). > > In those cases, the overlap period may not be very short (years vs. > weeks/months). > > I have also seen some use one protocol (which I think was mentioned in > another response) used for IPv4 and another used for IPv6. The cases I am > familiar, tended to be IPv6 with IS-IS and IPv4 with OSPFv2. > I guess the reasoning here was that if you are running dual stack, with > OSPF you will need to run two protocols anyway, so running OSPFv2(IPv3) > and OSPFv3(IPv6) may not be that different then running OSPFv2(IPv4) with > IS-IS(IPv6). This dual stack option has run longer or is semi-permanent > at times. > > A sub-case to the above may also be that one (operator) may want to > leverage some of capabilities of IS-IS and may not be willing to get off > OSPF for some reason. The Multi-topology option in IS-IS may be quite > useful if you have some functions which are non-congruent in your network > and you want to maintain topology variations (multicast being one, or > in-band management which I believe was alluded to in your OOB use case) > > Regards, > > Victor K > > > > On 2013-05-12 4:41 AM, "Glen Kent" <[email protected]> wrote: > >> >Hi, >> > >> >I would like to understand the scenarios wherein the service >> >provider/network admin might run both ISIS and OSPF together inside their >> >network. Is this something that really happens out there? >> > >> >One scenario that i can think of when somebody might run the 2 protocols >> >ISIS and OSPF together for a brief period is when the admin is migrating >> >from one IGP to the other. This, i understand never happens in steady >> >state. The only time this can happen is if an AS gets merged into another >> >AS (due to mergers and acquisitions) and the two ASes happen to run ISIS >> >and OSPF respectively. In such instances, there is a brief period when two >> >protocols might run together before one gets turned off and there is only >> >one left. >> > >> >The other instance would be when say OSPF is used to manage the OOB >> >network >> >and the ISIS is used for network reachability. >> > >> >Is there any other scenario? >> > >> >Glen > >
