nanog mailing list archives
Re: ISIS and OSPF together
From: Glen Kent <glen.kent () gmail com>
Date: Mon, 13 May 2013 00:13:38 +0530
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 <victor () jvknet com> 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" <glen.kent () gmail com> 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
Current thread:
- ISIS and OSPF together Glen Kent (May 12)
- Re: ISIS and OSPF together Peter Ehiwe (May 12)
- Re: ISIS and OSPF together Mikael Abrahamsson (May 12)
- Re: ISIS and OSPF together Randy Bush (May 12)
- Re: ISIS and OSPF together vijay gill (May 19)
- Re: ISIS and OSPF together Victor Kuarsingh (May 12)
- Re: ISIS and OSPF together Glen Kent (May 12)
- Re: ISIS and OSPF together Scott Morris (May 12)
- Re: ISIS and OSPF together Victor Kuarsingh (May 12)
- Re: ISIS and OSPF together Randy Bush (May 13)
- Re: ISIS and OSPF together Glen Kent (May 12)
- Re: ISIS and OSPF together Måns Nilsson (May 12)
- Re: ISIS and OSPF together Jen Linkova (May 15)
- Re: ISIS and OSPF together Jayram Deshpande (May 15)
- <Possible follow-ups>
- Re: ISIS and OSPF together Brandon Butterworth (May 19)