Jeff Squyres wrote:
On Feb 12, 2007, at 12:54 PM, Matteo Guglielmi wrote:

This is the ifconfig output from the machine I'm used to submit the
parallel job:

It looks like both of your nodes share an IP address:

[root@lcbcpc02 ~]# ifconfig
eth1      Link encap:Ethernet  HWaddr 00:15:17:10:53:C9
          inet addr:  Bcast:  Mask:
[root@lcbcpc04 ~]# ifconfig
eth1      Link encap:Ethernet  HWaddr 00:15:17:10:53:75
          inet addr:  Bcast:  Mask:

This will be problematic to more than just OMPI if these two  
interfaces are on the same network.  The solution is to ensure that  
all your nodes have unique IP addresses.

If these NICs are on different networks, than it's a valid network  
configuration, but Open MPI (by default) will assume that these are  
routable to each other.  You can tell Open MPI to not use eth1 in  
this case -- see this FAQ entries for details:

Those nic "eth1" are not connected at all... all the machines use only the eth0
interface which have different IP for each PC.

Anyway you solved my problem suggesting me those FAQ entries!!!
--mca btl_tcp_if_exclude lo,eth1

that's the magic option which works for me!!!

Thanks Jeff!!!