[K12OSN] Window Clients can't get past the Linux Server

[jones yeates]

I have a K12LTSP server up and running off of Fedora Core 5.  We are using a 
floppy disk to boot onto the Linux server, and it is working well.  We have 
Internet connection as long as the clients boot in Linux.

When we take the floppy out, the clients boot up in Windows.  However, the 
clients can't get access out of the LAN.  The server (acting like a router) 
isn't letting the clients through.

I've tried changing the /etc/sysctl.conf file's line for ip forwarding:
net.ipv4.ip_forward = 1
Then I typed:  /etc/init.d/net.eth0
Everything started up fine.  Still no luck.

I also have nat running and it seems to be working fine as well (as far as I 
can tell).

There is a firewall, and I'd like to keep it on.  I noticed that someone 
else had the same problem and resolved it by turning the firewall off 
(https://www.redhat.com/archives/k12osn/2007-April/msg00012.html), which is 
something I'd rather not do. The trusted services are HTTP, HTTPS, FTP, and 
SMTP.

I also saw something about
chkconfig --level 345 transparent-proxing on
at:  https://www.redhat.com/archives/k12osn/2007-August/msg00172.html

I would try it out but I am not sure how to reset the settings back to what 
I originally had, just in case I mess something up or it doesn't work or 
understand the chkconfig --list | grep prox  output.

Is there a way to fix this?  As you can tell, I'm new to Linux.

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