Subject: about v6 over multicast-less Ethernet

From: Alexandru Petrescu <[email-masked]>
Date: Mon, 28 Feb 2005 19:11:21 +0100

Hello,

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.

How should I go about it?

Thanks,

Alex
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From: "Manfredi, Albert E" <[email-masked]>
Date: Mon, 28 Feb 2005 15:36:49 -0500

> first place, but anyways.

Not sure I understand the problem.

For IPv4 multicast, the Ethernet address becomes 01-00-5E and the lowest 23 bits of the IPv4 Class D address.

For IPv6, 33-33 and the lowest 32 bits of the IPv6 multicast 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?

Bert