Last night I was setting up my new Time Capsule and suddenly lost access to all my remote servers over ssh.

All I got was the following error upon connection ‘ssh_exchange_identification: Connection closed by remote host” and everything I searched around the web implied this was to do with too many connections to the server or incorrect reverse dns setup.

Neither or these issues applied to me and for a while I was stumped until it dawned on me that the Time Capsule had a much better NAT implementation it in with specific handlers for different protocols and I have all my servers configured to accepting incoming ssh connections on a non-standard port so as to reduce the number of ssh probe attacks.  Once I opened up a different port that isn’t used for other protocols by default it all burst back into life.

Hopefully, this will help someone who encounters the same problem in the future!