On Wed, May 10, 2006 at 09:56:58PM -0700, Roland Dreier wrote: > Hal> Huh ? In this case, aren't the subnet prefixes are required > Hal> to be different ? > > It's kind of a crazy thing to do but I don't see anything in the IB > spec that forbids two subnets with the same subnet prefix, or any > reason why a router couldn't route between them. The SMs would just > have to be smart enough to return the LID of the router for paths to > ports on the other subnet, and the routers would have to have explicit > routes rather than forwarding based on just GID prefix.
Hmm, this is an interesting point, you can do this in IP land using host routes. How about this - the Path record (and related) SA responses include the Hop Limit fields and the spec says: 8.3.6 Hop Limit: [..] Setting this value to 0 or 1 will ensure that the packet will not be forwarded beyond the local subnet. So, it is within the spec to use HopLmt >= 2 as the GRH required flag. I'd propose that the combination of a non-link-local prefix and a >= 2 Hop Limit should force a GRH. SM's that do not support routers should always fill in 0 for HopLmt. Jason _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
