A bit more information might make it easier to give useful answers. You did say network. Multiple machines? Servers? How many? Single tape drive? Stacker? Library?
Simple answers might be something like:
http://www.faqs.org/docs/linux_admin/backups.html. But, that doesn't tell you how to deal with the tape drive. Try `man mt` if you aren't familiar with it. You'll need to know the device name.
If what you find there is inadequate for your needs, and you have multiple machines to backup, then you could take a look at Amanda:
http://www.linuxquestions.org/bookmarks/tags/zmanda. There is a quick start guide on their wiki that can get you going.
