SSH No Longer Working After Sierra Update I'm trying to ssh into a remote server using the format: 

user@ip -i ~/.ssh/path/to/key 


and I get the following error:

/etc/ssh/ssh_config: line 55: Bad configuration option: gssapikeyexchange
/etc/ssh/ssh_config: line 56: Bad configuration option: gssapitrustdns
/etc/ssh/ssh_config: terminating, 2 bad configuration options


Connecting to a server without an SSH key doesn't work either.

Thanks.
Comment out or remove the lines

gssapikeyexchange no
gssapitrustdns no


from your /etc/ssh/ssh_config and you should be good.