Manfredi, Albert E wrote:
Alexandru Petrescu wrote:
Anyone proposed until now to update RFC2464 "IPv6 over Ethernet
Networks"? If not, I'd like to propose updating the following
text:
An IPv6 packet with a multicast destination address DST,
consisting of the sixteen octets DST[1] through DST[16], is
transmitted to the Ethernet multicast address whose first two
octets are the
value 3333
hexadecimal and whose last four octets are the last four octets
of DST.
Not all Ethernet links/cards/drivers/firmware support this 3333
value, nor even Ethernet multicast groups. Those who don't will
work fine with v4 (6 times ff) but not with v6. So some relaxing
text saying "either 33:33:xx:xx:xx:xx or ff:ff:ff:ff:ff:ff" may
help.
I don't understand why ND is so tight to the Ethernet multicast in
the first place, but anyways.
Not sure I understand the problem.
Not sure I understand the problem myself either. It's just that RAs are
sent to 33:33:0:0:0:1 and some cards don't get the packets addressed to
that (but they do get the packets addressed to ff:ff:ff:ff:ff:ff).
Remark all-ff is what DHCPv4 uses.
Whether cards not receiving 33-addressed RAs is a common problem or not
- I don't know, I'm asking.
For IPv4 multicast, the Ethernet address becomes 01-00-5E and the
lowest 23 bits of the IPv4 Class D address.
A certain DHCPv4 implementation uses all-ff for broadcasting.
For IPv6, 33-33 and the lowest 32 bits of the IPv6 multicast address.
Yes, but what happens when the Ethernet below does not support
multicast? Where are all the IPv6-multicast-addressed packets sent to
when the Ethernet below does not support multicast? Shouldn't they be
sent to the broadcast address?
Don't all Ethernet cards and drivers understand the meaning of the
LSbit of the first byte (the G/I bit)? As long as that bit is set to
1, won't all Ethernet switches know to flood the frame to all ports
in the spanning tree?
May be so, I don't know.
Alex
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