Are you getting this error message when connecting to a SSH Server from your MACOS?
Unable to negotiate with x.x.x.x port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1
Since the upgrade of El Capitan (10.11) to Sierra (10.12), MAC OS has upgraded their OpenSSH version from 6.9 to 7.2. This change deprecated a number of algorithms by default. This included diffie-hellman-group1-sha1 which is used on most Cisco routers, firewalls and switches.
In order to enable legacy support, perform the following.
- Edit or create a new file
- Put this entry in the file