ADSL and private network behind FireBrick

					ADSL non-NAT installation Internal machines on private addresses Port mapped incoming SMTP email

In this configuration there is a routed non-NAT internet feed (e.g. ADSL). The PCs are to be on private addresses. In this example we will assume that the ADSL router has address 123.4.5.1 and the subnet is a block of 16 (/28 or 255.255.255.240).

The FireBrick provides a NAT configuration to private addresses :-

1. Allocate a private network address for the internal machines, e.g. 10.0.0.0/24
2. Allocate the FireBrick a private address, e.g. 10.0.0.1 creating a LAN subnet for the FireBrick on this address and subnet 24 (255.255.255.0), set NAT
3. Optionally, include DHCP allocation range on the private addresses to allocate addresses to machines on the LAN
4. Allocate the FireBrick one of the public addresses, e.g. 123.4.5.2 and create the WAN subnet with this address, subnet 28 (255.255.255.240)
5. Set the gateway on the FireBrick to the router on the WAN (i.e. 123.4.5.1)
6. PCs are set with the FireBrick as their gateway (i.e. 10.0.0.1) and subnet 24 (255.255.255.0)
7. You may want to set the FireBrick with an ISP allocated DNS server address, and set the PCs to use the FireBrick for DNS (needed for DHCP use)
8. Adjust filters as required

1. Any installation with a router and a single subnet
2. e.g. BT net start lines