OSX: Mimic Ubuntu IP Masquerading via iptables with ipfw
- by Dogbert
Good day,
I am attempting to replicate a setup I have between a router and an Ubuntu PC, and have the same setup working on my MacBook (10.6, Snow Leopard).
First, I have a router that has a USB port. When I plug it into my Ubuntu PC, it creates an RNDIS connection, allowing me to connect to the router over the USB cable via an IP connection. When I plug it into my computer via USB, it gets assigned an IP address of 172.16.84.1, and a new adapter appears when I type ifconfig. I can then SSH into the device via ssh [email protected].
When I log in to the device, I flush the routes, then create the default route:
admin@localhost> route -f
admin@localhost> route add default 172.16.84.2
Now, in my Ubuntu machine, I use iptables to enable IP masquerading:
root@Valhalla> sudo iptables -t nat -A POSTROUTING -s 172.16.84.2 -j MASQUERADE
Once this is all done, the router has internet access over the USB connection to my PC.
I am trying to replicate this exact setup on my MacBook now (Snow Leopard), but iptables does not exist for OSX, not even a Macports version exists. I have scoured through other questions on StackOverflow that cover the usage of the ipfw command, which apparently works as a drop-in replacement for iptables. However, the syntax is significantly different, and I'm pretty much lost.
Does anyone with some experience with ipfw have some suggestions on how I could accomplish this and create a NAT connection via IP masquerading like I could with my Ubuntu PC?
Thank you for your assistance.
