IP Masquerading not working! HELP!

IP Masquerading not working! HELP!

Post by Toby Re » Mon, 09 Dec 1996 04:00:00

I have a Slackware 3.0 system running Linux 2.1.14. NE2000 ethernet card,
IPFWADM 2.3.0, IP firewalling, Firewalls, IP forwarding/gatewaying, IP
masquerading, etc. compiled into the kernel.

I install the modules and use ipfwadm as follows:

/sbin/depmod -a
/sbin/modprobe ip_masq_ftp.o                    # Non-PASV FTP transfers
/sbin/modprobe ip_masq_raudio.o                 # Realaudio audio streaming
/sbin/modprobe ip_masq_irc.o                    # Internet Relay Chat
/sbin/modprobe ip_masq_cuseeme.o                # CU-See-Me video conferencing
/sbin/modprobe ip_masq_vdolive.o                # VDOLive live video streams

/sbin/ipfwadm -F -p deny
/sbin/ipfwadm -F -a m -S -D

When I go to a WFWG machine with TCP/IP installed and configured, and a
PPP connection up with pppd, I telnet to an internet host, and it says
"connecting to blah.com" and just sits there for 60 seconds until it times
out. On the linux  machine, it shows

ipfwadm -F -l

acc/m  from to anywhere (ports: N/A)

and it shows an ip masquerading entry (ipfwadm -M -l) for that connection,
but nothing happens. I've read the howto a kazillion times and I can't
figure out what I'm missing. Modules-2.1.18, Latest libc and gcc. pppd

Netstat shows nothing at all......but I spose that could be its regular

I'm desperate to get this working before XMAS!

Someone help! please! ;)


only 20% of messages get thorough. No kidding!


1. IP Masquerading works, but does not masquerade from within the local network

I've got a box running Redhat 6.1 working as a gateway for our home network.
It's connected to a cable modem, and we've only got one IP address, so it's
doing IP forwarding and masquerading for us.

Now, consider this situation: I've got a webcam running on one of my windows
boxes, whose IP address is (for instance). The webcam is on port
8888, and I've got the linux box set up to forward this port along from
port, say, 9999, using a line much like

ipmasqadm portfw -a -P tcp -L xxx.xxx.xxx.xxx 9999 -R 8888

in my rc.local.

This works very well for people connecting in from outside - they'd use a
URL like:


but if I try and use that URL from inside the local network, it doesn't
connect, I'd have to use:

which is rather annoying as it makes it difficult to test things (I have to
VNC out to work and boot up a browser there)

I'm fairly sure the problem isn't with the webcam software - I've had the
same problem when trying to connected to an apache server inside the network
as well.

any ideas?



2. REQ: Help with talkd AND X11

3. IP masquerade -- does not work --help

4. Q: Why does my X-server allocate 175 MB during start up?

5. Help! IP-Masquerade not working, but ICMP does?!?

6. Redirect / Forward Concepts

7. IP Masquerading not working

8. CA questions

9. telnet not work with ip masquerading

10. IP masquerading not working, but DNS names resolve

11. @home cable not working with IP masquerading

12. Q: IP Masquerading not working, what to look?

13. DX _6_ Zone game through Linux IP Masquerade and IPFWADM not working