[openib-general] question regarding GRH flag in ib_ah_attr

[Hal Rosenstock]

On Thu, 2006-05-11 at 13:29, Roland Dreier wrote:
>     Sean> We currently use ARP to resolve an IP address to a DGID,
>     Sean> which I don't believe will work across a router.  Does an
>     Sean> app even know enough to be able to get a path record?
> 
> I think you're fine.  The IB router just has to handle forwarding
> multicasts

Specifically IPoIB broadcast

>  between two IB subnets for ARP to work.

Yes, because an IPoIB subnet can span multiple IB subnets.

> If there's also an IP router in between the two hosts

when the hosts are on different IP(oIB) subnets.

> then there's a problem, but I don't think it's that reasonable 
> to expect to make a direct RDMA connection in that case.

That's a different case; you don't ARP off your IPoIB subnet; you get
the next hop router towards that IPoIB subnet.

-- Hal

>  - R.