Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!hsdndev!bu.edu!wang!fitz From: fitz@wang.com (Tom Fitzgerald) Newsgroups: comp.dcom.lans Subject: Re: 10Base-T hubs Message-ID: Date: 18 Apr 91 06:04:35 GMT References: <1991Apr10.150801.2519@ux1.cso.uiuc.edu> <1991Apr15.214932.9635@jhereg.osa.com> <1991Apr16.182217.6151@netcom.COM> Distribution: usa Organization: Wang Labs, Lowell MA, USA Lines: 28 jbreeden@netcom.COM (John Breeden) writes: > I've been paying around with a new hub - AT&T's "smart" hub [...] > But the most interesting feature is this - a frame sent to a specific > mac address only shows up at the port that mac address is attached to. All > other ports get the header with the data field blank! (filled with 1s & 0s) > - you can't capture other people's traffic! only your own! You mean, you can't receive any packets until you've sent at least one packet out? Sounds like it could cause problems. If you clear the hub's memory while systems are attached to it, 2 machines that were talking to each other will be locked out of communication until they both send unsolicited packets and the hub figures out where they are. Protocols that depend on systems knowing each others' MAC addresses would have real problems at boot time. (Broadcast-oriented protocols should be ok). I'll bet you could get around this anyway, if you had a PC with a flexible enough interface card. Send out a lot of packets with different source addresses, i.e. all the mac addresses that you know of on the same ethernet that aren't attached to the same hub. The hub will think that all those nodes are on your port, and will give you the data. Of course, this will show up on your map. --- Tom Fitzgerald Wang Labs fitz@wang.com 1-508-967-5278 Lowell MA, USA ...!uunet!wang!fitz