Verified answer

Hmmmm...... Good question!! And in some cases below, the backup media should be a pencil and paper.

By "restore a network", what exactly do you mean? Does a server crash, where the server is the router, runs DHCP and DNS constitute a network crash?

1) Backup your router. On some routers you can export your routers configuration to an XML file. You should back that up periodically. Even if it doesn't change, you want to be sure what ever backup medium that you use, always has a copy of the router configuration on it.

2) DHCP configuration. For most home and small office networks, DHCP is on the router. But for most server-based networks, DHCP is a service on the server. As a minimum you should fully document the DHCP settings.

3) DNS configuration. For server-based networks, DNS is how computers find each other on the network. If you have created any special DNS entries, then you won't want to forget them when you're restoring a dead server.

4) Corporate data files. A network with one or more file servers, you should back up all of these files. You want your users to save all of their work to the servers, yet in the event of a failure you want to be able to recover these files. This would include SQL Server / Oracle / MySQL databases or whatever databases if you're not using a Windows environment. This would also include Exchange server mailboxes etc.

5) usernames and passwords for all installed applications.