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
Ospf offered as Pe-ce protocol to L3 mpls vpn customers and Isis as IGP for MPLS Core. Sent from my iPhone On May 12, 2013, at 9:41 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
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.
no. some ops come to see the light and move their network from ospf to is-is. see vijay gill's nanog preso http://nanog.org/meetings/nanog29/presentations/aol-backbone.ram
Randy is correct. In most cases, the two protocols are running co-incident for a while so you can do your table validation and topology mapping and then you turn off OSPF. For vendors that aren't capable of supporting ISIS, this is a feature and not a bug. On Sun, May 12, 2013 at 1:57 AM, Randy Bush <randy@psg.com> wrote:
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.
no. some ops come to see the light and move their network from ospf to is-is. see vijay gill's nanog preso http://nanog.org/meetings/nanog29/presentations/aol-backbone.ram
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
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
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 <glen.kent@gmail.com> Date: Mon, 13 May 2013 00:13:38 +0530 To: Victor Kuarsingh <victor@jvknet.com> Cc: "nanog@nanog.org" <nanog@nanog.org> 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 <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
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.
and, as is-is supports 4 and 6, why do you use ospf in this scenario? randy
Subject: ISIS and OSPF together Date: Sun, May 12, 2013 at 02:11:37PM +0530 Quoting Glen Kent (glen.kent@gmail.com):
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?
Indeed; one of the more sane situations might be to have say anycast name servers or full-service resolvers in the network and having them talk OSPF to the first hop router. ISIS daemons on PC operating systems are scarce, working ones hardly exist. It is clear, though, that the path forward is ISIS; most people I've spoken to roll it out (in greenfield/forklift situations) or migrate to it. -- Måns Nilsson primary/secondary/besserwisser/machina MN-1334-RIPE +46 705 989668 I always have fun because I'm out of my mind!!!
On Sun, May 12, 2013 at 6:41 PM, Glen Kent <glen.kent@gmail.com> wrote:
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.
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?
There is still equipment around which doesn't support ISIS but support OSPF. Getting such boxes into a network which is using ISIS might lead to running both protocols together. -- SY, Jen Linkova aka Furry
Sent from my iPhone On May 12, 2013, at 1:41 AM, Glen Kent <glen.kent@gmail.com> wrote:
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?
Yes, in virtualization world , where people no more want to waste their links that form loops, there are scenarios where you may have a TRILL deployment that runs over IS-IS while you have OSPF running side by side. -Jay
participants (10)
-
Glen Kent -
Jayram Deshpande -
Jen Linkova -
Mikael Abrahamsson -
Måns Nilsson -
Peter Ehiwe -
Randy Bush -
Scott Morris -
Victor Kuarsingh -
vijay gill