Date: Thu, 23 Oct 2003 14:23:57 -0400 From: Charles Swiger <cswiger@mac.com> To: net@freebsd.org Subject: Re: Help Broadcasting a UDP packet on the LAN:URGENT Message-ID: <109F1559-0586-11D8-92E1-003065ABFD92@mac.com> In-Reply-To: <20031023155247.GA6635@pit.databus.com>
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On Thursday, October 23, 2003, at 11:52 AM, Barney Wolff wrote: > On Thu, Oct 23, 2003 at 01:55:55AM -0700, Wes Peters wrote: [ ... ] > What are you going to do when IPv6 comes into more general use, since > it has no broadcast address? Are you asking what a IPv4-to-IPv6 translator (like gif?) should do, or are you worried about the case of a machine configured for IPv6 only and not for IPv4? I expect that most people will be using IPv4 for quite some time; we don't have to do something for the IPv6-only case to still have this be useful. >> Interactions with VLANs, for instance. If you send an >> all-ones broadcast on an interface that has one or more VLANs >> configured, >> do you repeat them "on" each VLAN as well? Ugh. What about >> point-to-point links? Are those always considered gateways to a >> foreign >> network, or just another form of locally attached network? > > The multicast notion would suggest that this be handled as a special > case of multicast, with a pseudo group that can't occur naturally. > That way you get "for free" to control which interfaces should send > the broadcast, based on group membership. Multicast and broadcast addressing are working at layer-3, but the point of using VLAN tags is to create logically 'seperate' networks where the flow of traffic is being handled/segregated at layer-2 rather than layer-3. > The whole VLAN thing is nasty, but I'd say that the general issue is > does the box itself have a virtual interface on the VLAN, or is it > merely switching on it. If the former, you send packets and process > received packets up the stack. If the latter, you just do what any > switch/bridge would do, because "you" (ie, higher layers) are not > really > on that layer-3 network. The all-ones broadcast is supposed to go to all physically connected network segments, regardless of whether a particular interface is ifconfig'ured with an IP that is part of a particular layer-3 subnet. You should be able to send the broadcast packet out from an interface which is up but does not have an IPv4 address assigned, right? -- -Chuck
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