Enable older SSH key exchange methods

When connecting via SSH to older systems who do not support newer ciphers, you will sometimes get the following error:

Unable to negotiate with port 22: no matching key exchange method found. Their offer: diffie-hellman-group14-sha1

To permanently enable support for this cipher, you need to add the following line to either /etc/ssh/ssh_config to enable it for all accounts or ~/.ssh/config for just your account.

Host * 
   KexAlgorithms +diffie-hellman-group14-sha1

You can change Host * to specify a specific IP. Ex: Host

More docs from OpenSSH Legacy Options.