The eth-multiplexer translator lets one share an ethernet device. It is commonly used to set up subhurds' networking to share an ethernet device with the subhurd and the main hurd. The subhurds' page has a guide to show you how to do this.

Here's a basic example to get you started using the eth-multiplexer. To do so, install the multiplexer at /dev/eth0m.

# settrans -c /dev/eth0m /hurd/eth-multiplexer --interface=/dev/eth0

Then configure your main Hurd system to use the virtual network interface /dev/eth0m/0 instead of /dev/eth0. On Debian/Hurd, this can be accomplished via:

# ifdown /dev/eth0
# sed -i -e s_/dev/eth0_/dev/eth0m/0_ /etc/network/interfaces
# ifup /dev/eth0m/0

Now you are all set to follow the subhurd's guide to set up a subhurd's networking! If you want to do more cool stuff with the eth-multiplexer, then you could take a look at the lwip page or remap page.