On node4:

[root@node4 ~]# glusterd
[root@node4 ~]# gluster probe node3
unrecognized word: probe (position 0)
[root@node4 ~]# gluster peer probe node3
Probe failed
[root@node4 ~]# gluster peer probe node3
Probe on host node3 port 6969 already a friend
[root@node4 ~]# gluster peer status
Command Execution Failed
Command Execution failed
[root@node4 ~]# 

On node3

[root@node3 ~]# gluster peer probe node4
Probe successful
[root@node3 ~]# gluster peer probe node4
Probe on host node4 port 6969 already a friend
[root@node3 ~]# gluster peer status
Number of Peers: 1
hostname:node4, port:0, uuid:9b606654-e59c-4099-afb1-af931fa57e6d, state:4
[root@node3 ~]# 


Note that here I started glusterd on node3 after the 'peer probe' was issued on node4