[Click] HostEtherFilter and Multicast

[Bart Braem]

On Monday 21 May 2007 11:09, Pierre-Emmanuel Le Roux wrote:
> I think there is a problem with the HostEtherFilter module and multicast
> address handling.
>
> An ethernet address is multicast if the bit 0 of the first byte is set to
> '1'.

I believe indeed there is an error there, as the IANA states in 
<http://www.iana.org/assignments/ethernet-numbers>:

ETHERNET MULTICAST ADDRESSES

An Ethernet multicast address consists of the multicast bit, the
23-bit vendor component, and the 24-bit group identifier assigned by
the vendor.  For example, DEC is assigned the vendor component
08-00-2B, so multicast addresses assigned by DEC have the first
24-bits 09-00-2B (since the multicast bit is the low-order bit of the
first byte, which is "the first bit on the wire").

Another list of Ethernet multicast addresses is maintained by Michael
A. Patton and is accessible at:

    <URL:http://www.cavebear.com/CaveBear/ether-codes.html>
    <URL:ftp://ftp.cavebear.com/pub/Ethernet-codes>
    <URL:gopher://ftp.cavebear.com/00/pub/Ethernet-codes>

Ethernet                Type
Address                 Field   Usage

Multicast Addresses:

01-00-5E-00-00-00-      0800    Internet Multicast        [RFC1112]
...

All examples there do not work with the 0x80 mask. Although I find it very 
strange that no one else noticed this.

Bart
-- 
Bart Braem
PATS research group
Dept. of Mathematics and Computer Sciences
University of Antwerp
Campus Middelheim, G3.30
Middelheimlaan 1
B-2020 Antwerpen, Belgium
Phone: +32 (0)3 265.32.91
Fax: +32 (0)3 265.37.77
Web: www.pats.ua.ac.be/bart.braem
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