#1120695 openmpi-bin: Unable to find reachable pairing between local and remote interfaces

Package:
openmpi-bin
Source:
openmpi-bin
Description:
high performance message passing library -- binaries
Submitter:
J.L.G. Pallero
Date:
2025-11-15 08:25:02 UTC
Severity:
normal
#1120695#5
Date:
2025-11-14 20:50:29 UTC
From:
To:
Dear Maintainer,

Trying to execute a MPI program with mpirun that works a few days ago, it still works, but I obtain some strange messages I can't interpret. The messages are:

[geo-w540][[64946,1],2][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] [geo-w540][[64946,1],1][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],3][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],0][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],1][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],3][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],0][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],3][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],2][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],1][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],2][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
[geo-w540][[64946,1],0][../../../../../../opal/mca/btl/tcp/btl_tcp_proc.c:266:mca_btl_tcp_proc_create_interface_graph] Unable to find reachable pairing between local and remote interfaces
#1120695#10
Date:
2025-11-14 21:18:06 UTC
From:
To:
Hello. I had a similar problem some time ago, which I forwarded here:

https://github.com/hypre-space/hypre/issues/1194

Can you try this to see if the messages (which afaik are just warnings
and harmless) go away?

export OMPI_MCA_btl_tcp_if_include=lo

Thanks.
#1120695#15
Date:
2025-11-15 00:27:24 UTC
From:
To:
The definition of

export OMPI_MCA_btl_tcp_if_include=lo

makes dissapear the warning. What does it mean?

El vie, 14 nov 2025 a las 22:18, Santiago Vila (<sanvila@debian.org>) escribió:
#1120695#20
Date:
2025-11-15 08:22:51 UTC
From:
To:
It tells OpenMPI to only use the loopback interface (lo) for TCP
communication. In this way, MPI processes can only communicate with
each other on the same machine, not across a network. I assume you
have a single machine here, so the above variable will still allow you
to use OpenMPI normally.

[ Can we close this bug? The message you see is just a warning, it does
not affect normal operation ]

Thanks.