External access of a server behind Orange Sagem Livebox

To open a service behind the Livebox Sagem, do the following. I use SSH as example, with port 22, and I assume that you use the default configuration of the modem.

1. Open an account at dyndns.org (I assume you know what it is, or you can figure it out. It provides you a free, fix DNS name that can "follow" the changing IP address of the modem).

2. Log in the modem as admin (default password: admin) from a machine that is behind the modem:

http://192.168.1.1

3. Set up the dyndns access properties. Select the Advanced Menu -> Network -> DynDNS drop-down menu item. Add your dyndns user name, password and the DNS name that you selected. Press Apply, then Update Now to see if the DynDNS access is OK. You should see the green "Updated - IP updated successfully" line.
4. Now, you have two options. If you want to access the services of only one server, then you can make that particular server fully visible to the world by using DMZ. Mind that it is unsafe, because the firewall in the Livebox will not protect that machine. If you want this, then select the Advanced Menu -> Firewall -> Policies menu item, then click on DMZ host. Add the local IP address of the server, and check the checkbox. Press Apply. Done.

5. If you have more servers, or you want to protect your server with the Livebox firewall (recommended), then you must specify the services one-by-one. Select Basic Menu -> LAN Servers. At the bottom of the table, click on New Entry. 

• Give a name to the service (arbitrary)
• Access activated: yes
• From port: 22 (the SSH server will be available on _your_dyndns_name_:22 for the world)
• To  port: the SSH port of the SSH server (22)
  
• Local IP address: the address of the server

Press Apply, and you are done.

Mind, that for an unknown reason, you cannot access the services with the dyndns name behind the Livebox. Try if from a real external machine (ex. ssh to an external server, and try ssh back to your server).