[root@onyx-28 ~]# lnetctl net show -v
net:
    - nid: 0@lo
      status: up
      tunables:
          peer_timeout: 0
          peer_credits: 0
          peer_buffer_credits: 0
          credits: 0
          CPTs:  0
    - nid: 10.2.4.74@tcp
      status: up
      interfaces:
          0: eth0
      tunables:
          peer_timeout: 180
          peer_credits: 8
          peer_buffer_credits: 0
          credits: 256
          CPTs:  0

[root@onyx-28 ~]# lnetctl net add --net tcp --if eth0
add:
    - net:
          errno: -22
          descr: "cannot add network: Invalid argument"

Lustre: DEBUG MARKER: == sanity test 24v: list directory with large files (handle hash collision, bug: 17560) == 12:10:03 (1415218203)
LNetError: 31891:0:(api-ni.c:1488:lnet_startup_lndnis()) Net tcp is not unique
LNetError: 31897:0:(api-ni.c:1488:lnet_startup_lndnis()) Net tcp is not unique
LNetError: 31899:0:(api-ni.c:1488:lnet_startup_lndnis()) Net tcp is not unique

 - created 10000 (time 141521821Lustre: DEBUG MARKER: cancel_lru_locks mdc start
3.63 total 10.13 last 10.13)
 - created 20000 (time 1415218224.04 total 20.54 last 10.41)