[openib-general] question regarding GRH flag in ib_ah_attr

[Hal Rosenstock]

On Thu, 2006-05-11 at 00:56, 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,

There's errata against the current confusion in the IBA spec in terms of
GID v. subnet prefix.

The bottom line on this is:

Each subnet is uniquely identified with a subnet ID known as the 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.

Assuming the above is ignored (and the subnet prefixes are not unique),
the routers along any particular path would just have explicit routes
for one of these duplicate subnets, right ?

-- Hal

>  - R.