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Subject: Re: [OMPI users] Returned "Unreachable" (-12) instead of "Success" (0)
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-05-18 07:22:11

On May 18, 2012, at 4:02 AM, devendra rai wrote:

> Hello Community/Ralph=0A=0AI was told by the sysadmin that the firewall doe=
> s not prevent communication between two machines (tik33x, tik34x) for insta=
> nce. However, it will only block if OpenMPI is trying to open TCP/UDP ports=
> lower than 1024, which require privileges.=0A=0AIs it possible to know whi=
> ch port numbers does OpenMPI use?

Open MPI uses random TCP ports above 1024 (i.e., we let the system assign which port numbers we use).

> Specifically, is it possible to specify p=
> ort numbers that OpenMPI must not use (OpenMPI-1.4.x)?=0A=0AHere is the rep=
> ly I got from my sysadmin:=0A=0A"There is a firewall, but it does not block=
> internal=0Atraffic within the whole TIK network (I verified it for myself)=
> .=0AThus, the connection problem must be somewhere else=0A(a service not ru=
> nning or binding to the wrong interface=0Afor instance). Maybe the service =
> wants to bind to a=0Atcp or udp port lower than 1024, which can only be=0Aa=
> llocated by the system's superuser. First, check on=0Awhich ports and on wh=
> ich network card interfaces=0Athe software listens and if it is configured =
> correctly=0Aso that it will listen at all."=0A=0A=0AIs there a way out?=0A=

You might try specifying exactly which interfaces Open MPI should use. For example:

mpirun --mca btl_tcp_if_include eth0 --mca oob_tcp_if_include eth0 ...

This would restrict Open MPI to only using the "eth0" interface (obviously, you should substitute in whatever is the relevant interface name for your machines -- hopefully, it's the same interface name across all of them).

Also, we just released Open MPI 1.6. You might want to upgrade when you can; the 1.6 series replaces the 1.4 series.

Jeff Squyres
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