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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