You could also add FreeSco to your list of choices.  From others on this list it
looks like a very useful OS for a Firewall/Gateway on a 486.  Running it
headless is a good idea so that if hacked they can't do much to it (like booted
from a CD image).

http://www.freesco.org/

> I recently obtained a 486 (Old Acer tower), with lots of nifty stuff: and
> old QIC-80 tape backup drive, 16 MB of RAM, coprocessor, and a CD-ROM. Only
> thing it didn't have is a hard drive, which I can add if necessary. The
> computer even has two 3Com Etherlink III cards. One with an and rj-45
> socket, the other with a serial style port for an external box and a coax
> socket. There's also an internal ISA modem, but I haven't managed to find
> any information on it yet, but I suspect it's probably not going to be fast
> enough that I'd want to use it for any great length of time.
> 
> As it's a shame to let a still working machine go unused, and since it's
> much quieter than my old Pentium 100 box I'm hoping to use it as a gateway
> for my home network. Currently I'm looking at Smoothwall, E-Smith and
> Coyote Linux.  While I have occasional access to a computer with a DSL
> connection I'm connected here at home over a plain old 56k modem (external,
> so I can move it over to the 486); so, since I beleive I've heard people
> here say they've used all three of those I thought I'd ask for comments
> before taking the time to download one or more of them.
> 
> First, a floppy only system would be nice, but isn't a requirement. I've
> got a spare 800 MB drive sitting unused as an emergency spare. And it
> should run on a 486, but I don't expect that to be a problem :-)
> 
> My biggest desire is for a gateway that will connect to the internet only
> on request. That is by conscious decision, not simply because some dail on
> demand daemon noticed that someone on the network started up their email
> software and that it automatically tried to download the newest messages.
> We only have one phone line, so not unintentionally making it busy is
> important. I seem to recall from my looking at the three mentioned
> distributions that at least one could be set so you would connect and
> disconnect by going to a local web page and simply clicking on a button.
> Having the connection be dropped after a time out period would still be nice.
> 
> Anything past that is a bonus.
> 
> I suppose my biggest request is for comments on Smoothwall, E-Smith or
> Coyote linux from anyone who has used them. They all look good, at least
> from the information on their websites, but nothing beats hearing from
> someone with experience.