I have a linux server with 8 nodes. each node has 8 cores. I can run a parallel job on a single node successfully. However, it failed when the job is run on more than two nodes (namely use more than 8 cores). The error information is:

mpirun: hostname: localhost, ip returned: 127.0.0.1

mpirun: hostname: cu06, ip returned: 192.168.0.6

mpirun: Can't talk to a remote host with IP 127.0.0.1

mpirun: Change hostname or check IP configuration mpirun: hostname: localhost, ip returned: 127.0.0.1
mpirun: hostname: cu06, ip returned: 192.168.0.6
mpirun: Can't talk to a remote host with IP 127.0.0.1
mpirun: Change hostname or check IP configuration

The 6th node is named cu06, with IP 192.168.0.6.

Could you please tell me the reason? Thank you.