Re: pinging through IPMASQ

[Adam Williams <adam@xxxxxxxxxxxxxxxx>]

 From          : klug>klug-request
 To            : adam
 Subject       : Re: pinging through IPMASQ
 Date          : 10/28/99 08:58


>>You can't ping a device outside your private network if you have network
>>address translation in use (IPMasq). If I'm not mistaken (and I could be),
>>you are sending the ICMP packet out, but the server responding to the ping
>>can't send the reply to your PC behind the NAT. It thinks your IP address
>Not true, I use NAT every day for translation and I am able to ping servers
>outside the local 192.168 subnet.

Yes, IPMasq deals only with TCP & UDP,  ICMP is niether of those thus~
traceroute, ping, and some other low level diagnostic tolls will not work~
with only IPMasq,  you need to enable ICMP Masq as well.  THis may be~
as simple as installing a  module (ip_masq_icmp?) or may require a kernel~
compile.  It is an option under networking options if you run~
"make menuconfig" in /usr/src/linux.

>is that of your IPMasq box, so it stops there. I don't think
>(tracert?) or any other util that depends on ICMP will work outside your
>In short, you can ping any device on your private network, but not on the
>outside, if you are using network address translation (IPMasq).
>I'm not too familiar with IPMasq within linux.  But could it be that some
>type of IP Forwarding is not configured?
>Maybe the pings are getting stopped at his
>gateway and not forwarding across the local subnet on return.

Good Call!  This is exactly what is happening.