what you need is NAT (or "masquerade") and forwarding on the linux box that "shares" the connection to the win98 box...I use this method, but I have one old linux-box as a firewall, another as my own pc and one (my bros) that runs windows. everything works...you'll need iptables for this, and iptables-forwarding/NAT enabled in your kernel (probably is?)
so go and get iptables and install it....here: iptables.org
after this, you just add some rules to your iptables on the linux machine, that enable forwarding and masquerade the ip addresses so that the net works also on the other machine....I think the commands are some like these: (I just wrote them from what I remember...haven't touched on my firewall config for a while, but I think these do):
/sbin/iptables -A FORWARD -i eth0 -j ACCEPT
/sbin/iptables --table nat --append POSTROUTING --out-interface ppp0 -j MASQUERADE
/sbin/iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
that should work; the interface that accesses net is ppp0 (dial-up connection) and the interface that is shared to is ethernet device eth0. change if you need to....the first line enables forwarding (if eth0 wants something, the data is sent there and not to the linux box itself), second adds masquerading (so that the win-box's ip is translated so it seems like the one of linux-box's, and after data comes back, the translation is done backwards so that both machines kind of like use the same ip and there comes no problems with where the data should be sent) and the third line appends a new rule to accept everything that's being forwarded, if it's part of some known connection.
if you have not set any firewall (iptables) before, then do
/sbin/iptables --flush
before the three lines above. that "clears" the table....oh yeah, and one more thing: after you've done these, test that the net works. if it does, then you _must_ save these lines to some start-up script, like /etc/rc.local (unless some network script already exists), because otherwise they get erased at every restart.
this is a simple thing really...and sorry about the lack of GUI, but iptables is the best when it's in console - some firewall builder (GUI) could do this for you, but I'm not sure...this works and is easy
oh, and if that doesn't work that's above, post here...as I said, I just think I remember them so I might have forgotten some line (or was that third line even needed?)...haven't played with iptables for a while. but after those you don't need to set anything else, net just should work, if the network is already set....
EDIT: yeah, I did forget something
the third line is not needed now that I think of it really...but this one is needed:
echo "1" > /proc/sys/net/ipv4/ip_forward
to get the forwarding really start. so, to make it clear, here's what you do in console, as root:
/sbin/iptables --flush
/sbin/iptables -A FORWARD -i eth0 -j ACCEPT
/sbin/iptables --table nat --append POSTROUTING --out-interface ppp0 -j MASQUERADE
echo "1" > /proc/sys/net/ipv4/ip_forward
and that's all. now go to the windows-machine, open up a browser, check from your internet settings that an internet connection is first looked for from the _network_ and only if that doesn't exist, then the _straight_ connection. after this is all right, type some address in your browser and try if it goes
should.
and after you see it works, add those 4 lines above to some startup (init) script; if you don't know to which, add them to /etc/rc.local with some text editor of your choise.
