Web Data Not Getting Through

[Bill K.]

I don't know if this is a masquerade problem or what.
RedHat 7.2, kernel 2.4.7-10
On a 2 PC network, PC#1 has modem for dial-up (ppp0) and single NIC
(eth0). PC#2 has single NIC (eth0).
The problem:
On PC#1, no problem.
On PC#2, cannot get data from a relatively small number of sites, but
most work fine.
Example: Cannot load page from www.foxnews.com on PC#2, but page loads
fine from PC#1. I can ping it OK from PC#2, but browsers and wget hang
and get nothing (wget makes 0 byte index.html file).

I've tried ipchains AND iptables, various scripts, and the result is
always the same (or worse). I can't tell if the server isn't returning
anything or if my gateway isn't letting data through, but I see that the
data lights on the modem applet go dark when I try to access one of these
sites from PC#2.

This is driving me nuts! I'd greatly appreciate ANY ideas on this.

[Peter Graves]

I'll try to keep this short and pithy :)

I have some ideas although I'm no expert, the following applies to
RedHat 7.2.
1) Your security might be too high. type serviceconf and under firewall
you should be able to set eth0 as a trusted device (if an available
option). Allow all connections/ports for now, you can back them off when
you get it working. run /etc/rc.d/init.d/xinetd restart

2) I recommend iptables over ipchains. I hated switching to it at first
but figure I have to sooner or later. You shouldn't have to disable
ipchains because iptables automatically takes precedence on restart.
Here is my easy way to setup masquerading without using a script using
iptables based on several successful RH7.2 installs but I will customize
it for your situation:

1) It sounds like you already have modem ppp0 and NIC eth0 (private
network) working properly. Let's assume eth0 is set to 192.168.0.1

2) use linuxconf to enable routing

3) in /etc/rc.d/rc.local , add the following 3 lines at the bottom:
echo "1" > /proc/sys/net/ipv4/ip_forward
iptables --table nat --append POSTROUTING --out-interface ppp0 -j
iptables --append FORWARD --in-interface eth0 -j ACCEPT

4) restart your server (Or in your case just type,
/etc/rc.d/init.d/httpd restart and /etc/rc.d/init.d/xinetd restart)

5) cat /proc/sys/net/ipv4/ip_forward should return 1

cat /etc/sysconfig/network should read something like:
NETWORKING=yes
HOSTNAME=xxx.wsu.edu (Your hostname)
FORWARD_IPV4="yes"
GATEWAY="134.121.143.xxx" (Your ISP Gateway)
GATEWAYDEV="ppp0"

iptables -t nat -L will list your IP tables

6) Be advised this is not a very secure iptables configuration so have
a good firewall in place eventually.

3) Of course it could be an unrelated problem. foxnews.com crashes my
browsers way too frequently, both in linux and windows (netscape,
konqueror, and mozilla), but generally works. It could be that they use
additional ports or try to do a reverse lookup. I don't have a modem in
linux so I can't exactly replicate your problem but I hope this is of
some help to you. It has worked successfully for me on several installs,
the only difference is I use eth0 and eth1 instead of ppp0 and eth0, and
http://foxnews.com/oreilly/ works fine for me.