Originally Posted by a-j

Oops, I thought you wanted your internal subnet masks to be 255.255.255.248. I see now that that is the subnet mask of your external IP.
I think this is how you would likely setup the routers behind the hub -- which strikes me as an odd way to do things (I would probably put in a switch instead of a hub, or even a router but that setup is more complicated, and prone to configuration problems).

Network 1.2.3.0/29 (suppose this is the network assigned by your ISP)
Subnet mask (255.255.255.248, the /29 above)
Broadcast 1.2.3.7
External IPs: 1.2.3.1 - 1.2.3.5 (assuming you only have 5 of the possible 6)

Router 1:
external IP - 1.2.3.1 (suppose this is one of your external IPs)
subnet mask - 255.255.255.248
LAN Network - 192.168.1.0
LAN Broadcast - 192.168.1.255
LAN Subnet mask - 255.255.255.0
LAN IPs 192.168.1.1-192.168.1.254 (use as you wish or setup DHCP)


Router 2:
external IP - 1.2.3.2 (suppose this is one of your external IPs)
subnet mask - 255.255.255.248
LAN Network - 192.168.2.0
LAN Broadcast - 192.168.2.255
LAN Subnet mask - 255.255.255.0
LAN IPs 192.168.2.1-192.168.2.254

... Repeat procedure for routers 3-5

It's been a while since I did any networking so hopefully I haven't messed anything up. If anyone sees errors, please point them out.