I have no experiences with bootstrapping Haiku but according to my information networking connection is mandatory. The Haiku devs outsourced plenty integral parts to HaikuPorts, so they needs to be downloaded during the build process.
Bootstrapping is not an everyday task, it gets less testing, it could be broken on some host OS, etc., and if you really want to bootstrap Haiku, then first try to get as much information as possible about the bootstrapping process, the haiku code, the build process, etc, so just read the code.
But building Haiku isn't an everyday task, and bootstrapping absolutely not an easy ride so be prepared to bugs and problems. If you met with problems, you may get help at the Haiku mailing lists, but this isn't the right place for your questions.
BTW, according to the Bootstrapping guide you can't bootstrap Haiku from Haiku.