If you are attempting to ssh into the department and see the following message:
ssh_exchange_identification: Connection closed by remote
host, it may be because your client machine is not properly registered in DNS.
There is an area on the homepage (only visible if you are logged out) that will perform a check to determine if this problem my exist for your machine. This is useful if you're having trouble ssh'ing to our portal machines, as we check to ensure the incoming clients' forward and reverse DNS records match. This page works by taking the IP address you are connecting from, and performing a lookup of that address to get a host name. It then looks that name up via DNS and checks the resulting IP address against the one you're connecting from.
If the DNS check do not match, you will need to contact your ISP to ensure your hostname is properly registered.