When it comes to networking together UML instances there are plenty of options. The switch daemon or multicast allow us to have a purely virtual network and pcap allows us to monitor host traffic, but what if we want our UML sessions to appear as part of an external network? This could be the case if we were trying to provide some form of UML hosting solution for end users or we have service daemons that run inside UML sessions that we want our LAN, or even the internet, to see.

By implementing connectivity using bridging our UML sessions can have public or private (RFC1918) IP addresses and we have no need for any sort of special routing, either on the physical network or inside the UML instance itself. As far as the end-user or any daemons inside the UML are concerned, there is a normal ethernet adapter device the same as on a physical machine.