Am Montag, 10. Februar 2014, 14:33:05 schrieb RJ Atkinson: > Earlier, Karsten Thomann wrote, in part: > > I don't know if i have missed that part, but what would happen if OSPFv3 > > is running over IPv4 and there are two (or more) IPv6 Islands already > > deployed within the network, should there be any LSA flooding checks, > > like do not flood LSA with IPv6 networks over IPv4 only links, or should > > the route > > calculation/installation of the information simply fail > > as there is no valid path? > > The OSPF deployments I am familiar with did not "auto deploy" > or "self deploy". Instead, all of the OSPF deployments that I am > familiar with had engineers making deliberate decisions about how > to configure the OSPF deployment, and also how to configure the > OSPF routers in that deployment. I know that such deployments are normally well planned, but as there is already a draft about ospfv3 autoconfig, even if it is not designed to be used in company networks.
> One deployment option, already deployed in some places, is to run > "ships in the night". In this model, the IPv4 topology exclusively > uses OSPFv2 over IPv4 and the IPv6 topology exclusively uses OSPFv3 > over IPv6. For some sites, that is a good option. A number of my > clients are very interested in this new I-D because it optimises > their IPv6 transition strategy. > > For some sites, IPv6 transition is simplified, optimised, and also > cost-reduced by using OSPFv3 over IPv4 initially, and carrying both > IPv4 prefixes and IPv6 prefixes inside that one OSPFv3 deployment > (i.e. using the Address Family extension to keep the prefixes clearly > differentiated within a single OSPFv3 deployment). This can lower > operational costs because one can get by with managing only OSPFv3, > rather than having to manage both OSPFv2 and OSPFv3. > > If one's "IPv6 islands" (to use your term) are really dual-stack > (aside: having dual-stack rather than IPv6-only would be expected > and normal if another part of one's OSPF deployment is using > OSPF over IPv4), then EITHER the whole deployment should be configured > to run over IPv4 XOR the whole deployment should be configured > to run over IPv6. > > Having different "IPv4 islands" and "IPv6 islands" is an explicit choice > of a configuration engineer or design engineer. That probably is not > the optimal deployment choice for an engineer to make. It definitely > is NOT a choice that I would make or that I would recommend to my clients. I would not do it either, but I have already seen some strange ospf designs..., and as mentioned it is a case which can happen with ospf autoconfiguration, but we don't need to discuss it further as it is for homenetworks > From the descriptions and definitions in the draft, it would not be > "normal" or "expected" to mix IPv6 transport with IPv4 transport > within a single OSPFv3 deployment. > > > Is there any explicit preference over which version the adjacency > > is build if v4 and v6 is available in that specific part of the network? > > The choice of preferred OSPF transport really is something that the > configuration engineer ought to configure. As the details of configuring > any IP router are outside the scope of the IETF, I am not sure that > this I-D properly can or should say very more than it already says. > > Perhaps the I-D could add clarifying text along these lines > somewhere in Section 2: > > "Implementers of OSPFv3 over IPv4 SHOULD add a configuration > knob to let the router administrator select whether a given > OSPFv3-enabled interface should use OSPFv3 over IPv4 or > OSPFv3 over IPv6. Except when an OSPFv3 deployment is being > transitioned from using IPv4 transmission to using IPv6 > transmission, it is RECOMMENDED that all routers within an > OSPFv3 deployment use the same IP version for OSPFv3 packet > transmission." > > > What should happen when an IPv4 Link gets v6 added, graceful reestablish > > the adjacency over IPv6, or wait until forced protocol switch? > > See my answer just above. > > I would expect that any router that implements this I-D also would implement > a configuration knob to indicate whether IPv4 transmission or IPv6 > transmission is preferred. Over time, a configuration engineer might > change this (e.g. manually change from IPv4 transmission to IPv6 > transmission AFTER an entire IPv4 network has been > deployed-with/converted-to dual-stack IPv4 and IPv6). > > Yours, > > Ran Atkinson Thanks for the detailed anwsers, I'm satisfied with the addition. Kind regards, Karsten > > > _______________________________________________ > OSPF mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/ospf
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