Date: Sun, 27 Oct 2002 00:36:19 -0400 From: Don Bowman <don@sandvine.com> To: 'Julian Elischer' <julian@elischer.org>, Kevin Stevens <Kevin_Stevens@pursued-with.net> Cc: freebsd-net@FreeBSD.ORG Subject: RE: Annoying ARP warning messages. Message-ID: <FE045D4D9F7AED4CBFF1B3B813C8533701022D95@mail.sandvine.com>
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> From: Julian Elischer [mailto:julian@elischer.org] (removed as to why have two NICs on the same network, sending for general enlightenment of the list...) This is reasonably common in L2 switched Ethernet. You have a device which segments the traffic just fine with MAC learning. You have the cables all going to the desktops. You don't want to muck around with partially supported VLAN tagging @ the desktop. So you run another network overtop the same Ethernet. You probably wouldn't architect it up front for that (although I have in our lab, we use a cat6k for a virtual patch panel, but individual tests use whatever IP's they desire). @ the Ethernet level, addressing is only done via MAC address. Having two packets on the same wire with differing IP subnets is legal (in fact, you see it all the time with the destination or source address which is off your network). ARP's and all 1's broadcasts (e.g. DHCP) make a bit of a mess of such a network, but sometimes that's the lesser evil. This can also be seen, believe it or not, on a routed network, if you have something like spanning tree protocol which hasn't converged yet, but has been set for rapid convergence (which assumes the path isn't a loop until it discovers otherwise). Routers and switches are merging. --don (don@sandvine.com www.sandvine.com p2p) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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