Many parts of this article have been taken, updated and adapted from an old text about bridging, edited by Nick Sayer. A pair of inspirations are due to an introduction on bridging by Steve Peterson.

A big thanks to Luigi Rizzo for the implementation of the bridge code in FreeBSD and for the time he has dedicated to me answering all of my related questions.

A thanks goes out also to Tom Rhodes who looked over my job of translation from Italian (the original language of this article) into English.