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RE: I/G and U/L - what one comes first? [7:67266] posted 04/11/2003
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Priscilla Oppenheimer wrote:

> Token Ring chipsets actually never handled the I/G bit in the
> manner that IEEE expected them to and didn't use just that bit
> to identify a group address. Instead they also checked to see
> that the Functional Address bit, the most significant bit of
> the second byte, was set to 0.

That should have said most significant bit of the third byte. Alaerte
probably caught this, but I bet nobody else did!? :-)

It's byte 2, the third one if you start counting with byte 0.

Note, that I'm using non-canonical bit ordering to match how most Token Ring
documents do it, although not RFC 1469. (Maybe all RFCs use canonical
ordering, for that matter. IEEE 802.5 and other Token Ring docs don't,


> For IP multicast, because Token Ring implementations have this
> problem, you have to also make sure the Funcational Address bit
> is set to zero, but that is the topic of RFC 1469, which is the
> document that you reference above, and probably beyond the
> scope of your original question.
> Priscilla

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