How to specify multiple HostName/Port combinations in .ssh/config

I have multiple notebooks and workstations which pull and push from multiple Mercurial repositories on a central server. I usually use .ssh/config to set an alias:

Host repo-server
HostName server.somedomain
User user143
IdentityOnly yes
IdentityFile ~/hgkey
Port 156

... and some more options, you get the idea. I can then simply do a hg push ssh://repo-server//hgroot/someproject on every local repository, and I can change the server address and port in one place.

For workstations, this works fine, but the notebooks can access the server either from inside the network or from outside, using a different address and a different port. Is there any way I can specify multiple HostName/Port combinations so that SSH automatically tries them in order? This way, the users could push and pull without having to care about the correct address.

(of course, using a VPN would be the most correct solution)

Solution 1:

I'm afraid that is not possible with SSH.

You could possibly work around this using the ProxyCommand option of ssh, along with a custom script that creates a TCP connection to a server (using netcat), depending on how/where your notebook is connected. Something along the lines of:

#!/bin/bash
SSID=$(/sbin/iwgetid wlan0 -r)

case "$SSID" in
net1)
  nc <host1> <port1>
  ;;
net2)
  nc <host2> <port2>
  ;;
*)
  nc <host3> <port3>
  ;;
esac

Then, in your .ssh/config, you would need the following:

Host repo-server
  User user143
  IdentityOnly yes
  IdentityFile ~/hgkey
  ProxyCommand path-to-script