ip masquerading

[John Summerfield]

bruce wrote:
> hi...
> 
> i have a situation where i have a system with two connections, one wireless,
> one eth connetion. i can currently connect with the wireless ath0 to my
> network/internet/etc...
> 
> however, when i activate the eth0 at the same time, i can't access the
> network via ath0. as far as i can tell, i need to implement ip masquerade to
> have eth0 map, to ath0...
> 
> my test ip addresses are:
>  ath0 - 192.168.1.33
>  eth0 - 192.168.2.33
> 
> any thoughts/comments/pointers...

You don't need IP masquerading, unless this system's going to be a 
gateway to the Internet for other computers.

You don't need IP masquerading if some other device is already doing it. 
The other device does need enough routes to access everything connecting 
through it, but in the usual case (you only have one subnet) that's how 
it's working. In your case, I assume you're using a "hardware" router 
and it's IP address is 192.168.1.1 or 192.168.1.254 (these are defaults 
for some brands). If it can be configured to route traffic to 
192.168.2.33 via 192.168.1.33, then you don't need IP masquerading, you 
just need to configure the route.

You do need both interfaces active at the same time, and network manager 
cannot do that at present, I've just engaged in a lengthy discussion 
about that either on this list, or on -test.

I don't know whether network manager can be configured to do one network 
and not the other.

In addition to configuring both network interfaces to be active at the 
same time, you also need to enable forwarding in /etc/sysctl.conf

Here's script I run for myself, for a similar task. It doesn't show 
everything, and it won't suit you without some work.
[root at localhost ~]# cat bin/startrelay
#!/bin/bash
ifdown eth0
ifconfig eth0 172.17.0.1
route add -net 192.168.9.0 gw 172.17.0.19  netmask 255.255.255.0 eth0
service dhcpd restart

[root at localhost ~]#

ath0 in this system provides access to the Internet via a Linux system 
function as an Internet gateway. It's configured via system-network-config.

"ifdown eth0" takes down the configuration established by 
system-config-network for eth0, I don't want this configuration to be 
standard.


-- 

Cheers
John

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