Date: Mon, 27 Apr 1998 23:08:13 +0200 From: Stefan Esser <se@FreeBSD.ORG> To: =?iso-8859-1?Q?Dag-Erling_Coidan_Sm=F8rgrav?= <dag-erli@ifi.uio.no>, "Matthew N. Dodd" <winter@jurai.net> Cc: Hans Huebner <hans@artcom.de>, freebsd-hackers@FreeBSD.ORG, Stefan Esser <se@FreeBSD.ORG> Subject: Re: FreeBSD HA configuration / Ethernet address takeover Message-ID: <19980427230813.00205@mi.uni-koeln.de> In-Reply-To: =?iso-8859-1?Q?=3Cxzpra2jfxkl=2Efsf=40hrotti=2Eifi=2Euio=2Eno=3E=3B_from?= =?iso-8859-1?Q?_Dag-Erling_Coidan_Sm=F8rgrav__on_Mon=2C_Apr_27=2C_1998_a?= =?iso-8859-1?Q?t_11=3A00=3A58AM_%2B0200?= References: <Pine.BSF.3.96.980426233709.21511D-100000@sasami.jurai.net> <xzpra2jfxkl.fsf@hrotti.ifi.uio.no>
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On 1998-04-27 11:00 +0200, Dag-Erling Coidan Smørgrav <dag-erli@ifi.uio.no> wrote: > "Matthew N. Dodd" <winter@jurai.net> writes: > > I'm kind of puzzled at how this would be integrated with the > > SIOCGHWADDR/SIOCSHWADDR calls as you might also need a way of determining > > which hadware address to set/get :) > > No. You can set any arbitrary MAC address, but it will make a heavy > impact on network performance, since much of what is usually done in > hardware (discarding packets not meant for you) will have to be done > in software. No, not true. Ethernet chips usually don't hardwire the MAC address, but provide one (or more) register(s) that typically get initialised from a serial EEPROM. But that register may be written to, and there are Ethernet protocols that rely on that feature (DEC LAT, DECnet). Many Ethernet chips accept 16 addresses, including Multicast addresses. In addition to exact address matches, there is often a hash (using the Ethernet CRC algorithm and hardware) used to select N out of 64 to N out of 512 MAC addresses, leaving the exact address match to be done in software. Regards, STefan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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