in /var/log/secure Feb 28 22:24:54 CompName sshd[3456]: Unable to negotiate with 192.168.x.y port 54104: no matching cipher found. Their offer: 3des-cbc [preauth]
or
Feb 28 23:03:41 CompName sshd[3149]: Unable to negotiate with 192.168.x.y port 54290: no matching MAC found. Their offer: hmac-sha1 [preauth]
or
Mar 11 11:53:42 CompName sshd[14432]: Unable to negotiate with 192.168.x.y port 56889: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1 [preauth]
This problem could also occurs on AIX machine. In /var/log/authlog
Error is :
Unable to connect to remote machine
Environment
Release : 14.0 all versions
Component : Client Automation
Resolution
On Linux machine ;
1- Edit file /etc/ssh/sshd_config and
* add 3des-cbc in the cipher list (if Ciphers parameter is set)