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Subject: [OMPI users] How are IP addresses determined?
From: Barnet Wagman (bw_at_[hidden])
Date: 2011-02-16 23:56:09


I've run into a problem involving accessing a remote host via a router
and I think need to understand how opmpi determines ip addresses. If
there's anything posted on this subject, please point me to it.

Here's the problem:

I've installed opmpi (1.4.3) on a remote system (an Amazon ec2
instance). If the local system I'm working on has a static ip address
(and a direct connection to the internet), there's no problem. But if
the local system accesses the internet through a router (which itself
gets it's ip via dhcp), a call to runmpi command hangs.

This is not firewall problem - I've disabled the firewalls on all the
system that are involved (and the router).

It is also not an ssh problem. The ssh connection is being made and it
appears that the application has been launched on the remote system.
After the runmpi command has been launched locally, a ps on the remote
system shows a process

    orted --daemonize -mca ess env -mca orte_ess_jobid 1187643392 -mca
    orte_ess_vpid 1 -mca orte_ess_num_procs 2 --hnp-uri
    1187643392.0;tcp://192.168.1.101:35272

While I don't really understand the orted process, I assume this
indicates that a command to execute an app has been received and that
opmpi is trying to run it.

I suspect that the problem is related to the '--hnp-uri ...
tcp://192.168.1.101' argument. 192.168.1.101 is the address of my local
system on my local network (attached to the router), which of course is
not accessible over the net. It appears that opmpi is transmitting the
local (static) ip address to the remote host.

It would help to know how opmpi determines and distributes IP
addresses. And if there's any way to control this.

Any thoughts on dealing with this would be greatly appreciated.

Thanks,

bw