Date: Sat, 3 Mar 2001 19:25:12 -0800 From: "Ted Mittelstaedt" <tedm@toybox.placo.com> To: "Larry Berland" <stuyman@confusion.net> Cc: "John Baldwin" <jhb@FreeBSD.ORG>, "Doug Young" <dougy@gargoyle.apana.org.au>, <freebsd-questions@FreeBSD.ORG> Subject: RE: Promiscuous Mode ?? Message-ID: <001b01c0a45a$b8f5c3e0$1401a8c0@tedm.placo.com> In-Reply-To: <Pine.NEB.3.96.1010303105937.29820B-100000@euphoria.confusion.net>
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>-----Original Message----- >From: Larry Berland [mailto:stuyman@confusion.net] >Sent: Saturday, March 03, 2001 11:16 AM >To: Ted Mittelstaedt >Cc: John Baldwin; Doug Young; freebsd-questions@FreeBSD.ORG >Subject: RE: Promiscuous Mode ?? > > > > >On Fri, 2 Mar 2001, Ted Mittelstaedt wrote: > >> >[mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of John Baldwin >> >On 01-Mar-01 Doug Young wrote: >> >> Would someone please comment on the following. The machine is >> >> running fine so I don't believe its anything particularly bad, but I >> >> don't recall seeing that particular message previously. >> > >> >Do you use DHCP? Every time you get or renew a lease dhclient puts the >> >interface in promiscuous mode. >> >> No, it doesen't - DHCP is just another service, it requests via broadcast >> packets and listens for a unicast packet response on a specified port. >> > >Correct me if I'm wrong, but when you request a lease after you've first >come up (aka no IP) you put out in broadcast, and then the dhcp server >will reply to you via broadcast as well. However, since the client No - this is not an IP traffic thing yet. An Ethernet broadcast is all 1's in the destination MAC address space (ff:ff:ff:ff:ff:ff) but it carries the source MAC address with it. The DHCP server response is a unicast packet that has a destination MAC address of the client. >doesn't necessarily know the broadcast (as they don't know their address >or the network address) they'd be using 255.255.255.255 or 0.0.0.0 until >they did, which would mean the dhcp server is binding to those addresses, >instead of just its normal IP and the broadcast IP for the network. Or >maybe i'm just insane. Basically, the point of this insane rant (I've >been awake far too long) is that the dhcp reply initially must be >broadcast, since the client has no clue what to listen to otherwise. But >since the client doesn't even know the broadcast address, does that mean >it gets its reply on 0.0.0.0 or 255.255.255.255, or does it just go >promisc to get the reply on the normal broadcast address? Forget the IP numbering. All the IP number is, is a pointer into the ARP table for the mac address of the ethernet card your sending the packet to. >Lacking in sleep, >Laurence Berland >http://www.isp.northwestern.edu/~laurence > >PS Did the chapter from TFCNG in DN get cut off? > Yes, I'm sending them the completed chapter. They didn't get the chapter from me, they got it from my darling publisher. Ted Mittelstaedt tedm@toybox.placo.com Author of: The FreeBSD Corporate Networker's Guide Book website: http://www.freebsd-corp-net-guide.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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