CPU for firewall machine?

[John Ackermann <jra@febo.com>]

I'm putting together a box to serve as a Linux firewall.  It will have
three ethernet interfaces: one to an ISDN (soon, I hope, to be 384kb DSL)
router, one to an internal network with a handful of PCs and one Linux
box that serves as both my playtoy and a samba file server, and the third 
to two or three web/mail/etc. servers that will be visible to the outside 
world.  The traffic load on the network is generally going to be light, and
of course the internet feed is at a very modest speed.  But, the firewall 
will be doing ipmasq stuff for the private network, and there will be times 
when a lot of data is moving between the DMZ servers and the internal network.

I have a nice small box with a 486DX4/100 in it, and am wondering if that's 
sufficient horsepower for this sort of application, or whether I should be 
looking at a Pentium.

A second question arises from the fact that the DMZ network is all using 
100MB ethernet cards, talking to each other through a speed-sensing,
switching hub, and I suspect that I won't find an ISA bus 100MB ethernet 
card for a price I'm willing to pay.  Will there be a significant impact 
if the servers have to switch to 10MB mode to talk with the firewall (the 
internal network is all 10MB, so there's no issue on that side).

Thanks for any thoughts on this.

John Ackermann
jra@febo.com