Firewalling on Linux 2.4

[Christopher White]

Rob,

> > I'm doing simple firewalling
> 
> Hmm, looks like Masquerading...

Yep.

> 
> > :input ACCEPT
> > :forward DENY
> > :output ACCEPT
> > -A forward -s 192.168.110.0/0 -d 0.0.0.0/0.0.0.0 -j MASQ
> 
> Give this a try.  I stick it in /etc/rc.d/rc.local:
> 
> /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Yeah, that's what I thought I should do, too.  But I've run this exact
command and it's had no effect. I could not get through the firewall from my
Win2000 machine when I used this box as my gateway.  Yet
masquerading/routing worked when I was using ipchains.  When I run the above
command, then check the tables, nothing has changed:

# iptables -L                                         
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy DROP)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

> echo "1" > /proc/sys/net/ipv4/ip_forward

In Red Hat you change a variable in /etc/sysctl.conf:

net.ipv4.ip_forward = 1

and the file /proc/sys/net/ipv4/ip_forward gets the "1" put into it.

> 
> For more documentation, try:
> 
> http://netfilter.filewatcher.org/unreliable-guides/NAT-HOWTO/index.html

Been there, read that.  That's where I found the command you suggested.  It
just doesn't work.  I'm baffled.

Thanx!

--Chris