Try FREESCO
http://www.freesco.org/
Been using it for a couple of years to protect my intranet. No worries.
"FREESCO is based on the Linux operating system and incorporates many of the features of a full operating system into software that fits on a single 1.44 meg floppy diskette. With FREESCO, you can make:
* a simple bridge with up to 10 Ethernet segments
* a router with up to 10 Ethernet segments
* a dialup line router
* a leased line router
* an Ethernet router
* a dial-in server with up to 10 modems (with multiport modems).
* a time server
* a dhcp server
* a http server
* a ftp server
* a dns server
* a print server (requires TCP/IP printing client software)
FREESCO also incorporates firewalling and NAT which are resident within the Linux kernel to help protect you and your network. All of these features can be used in conjunction with each other or individually."