I need some high-level guidance. Once I get the gist of the idea I will be able to figure out the low-level details myself (I hope).

I have 4 computers behind a netgear router, 1 Windows 1 Mac and two linux boxes. They all get their IP address (192.168.1.xxx) from a netgear router. I use one linux box for developing web sites. I want to use the other as a backup file server, for all other boxes on my little network.

I use rsync for disk to disk mirroring on linux boxes. And I also use rsync to copy files down from remote sites with fixed IP addresses. But on my lan every box gets a slightly variable dhcp IP address from the netgear router, depending on who boots first. So I don't know how to tell the backup server to pull from the other boxes....don't know which box is which, as it were.

Perhaps the backup server should become the dhcp server instead of the netgear router. But then I still don't know which other box is which. The only way I could see that working is if the other boxes pushed files to the backup server, where the backup server somehow, someway, always ended up with a fixed IP address like 192.168.1.2 (or what ever).

What am I missing? What is the high level description for how this can be made to work?

the router probably has a way to assign static ip's to each pc/tablet/fone/... on your network.

also linux could be setup via network-manager to ask for the same ip each boot (i assume the same for windows/mac).

Yes it does. I just needed a finger pointed in the right direction.

There is a trick however. The DHCP setup on the router assigns a range of numbers for random assignment to computers on the local subnet, which must be set large enough to accommodate the expected load (I'll never need more than a half a dozen. A law office might need 3 dozen IP addresses). Any fixed IP address (like 192.168.1.200) matched to a specific MAC address (for some routers anyway) must be OUTSIDE the random dhcp range. Now it works. I have a linux file server with two large disks all computers on my network can save to.

Ask and ye shall receive. Thank you.