Let me clean up any confusion I may have created.
First of all, the low-order 23 bits of the ip multicast group id is
placed into the low order 23 bits of the ethernet address.
Taking the last 3 octets of the 224.163.163.45 address will
leave you 163.163.45. In most cases 163 does convert to A3,
however the second octet of the 224.163.163.45 address only
has 7 useable bits (when dealing with multicast only).
so translating to binary normally you would have:
10100011.10100011.00101101=163.163.45
8 bits 8 bits 8 bits
or A3-A3-2D using 24 bits of address space.
translating for multicast purposes would drop the first bit
of the second octet and give you the following:
0100011.10100011.00101101=35.163.45
7 bits 8 bits 8 bits
or 23-A3-2d using 23 bits of address space.
(note that 35 translates to 23 hex)
so, the complete mac address will be 01-00-5E-23-A3-2D
Hopefully this makes a little more sense..dj
""D. J. Jones"" <[EMAIL PROTECTED]> wrote in message
8vn10r$m8h$[EMAIL PROTECTED]">news:8vn10r$m8h$[EMAIL PROTECTED]...
> I stand corrected. You have to use the rightmost 23 bits not all 24.
>
> See ElephantChild's response..
>
> ""D. J. Jones"" <[EMAIL PROTECTED]> wrote in message
> 8vn06a$lms$[EMAIL PROTECTED]">news:8vn06a$lms$[EMAIL PROTECTED]...
> > I think the correct mapping should be:
> >
> > 224.163.163.45 = 01-00-5E-A3-A3-2D
> >
> > Here is a great URL at 3com by Chuck Semeria and Tom Maufer
> >
> > http://www.3com.com/nsc/501303.html
> >
> > I think this will give you a good idea of how to map (not convert) a 32
> bit
> > class D
> > multicast address to a 48 bit ethernet address.
> >
> > Hope this helps..dj
> >
> > ""Patrick A. Morin"" <[EMAIL PROTECTED]> wrote in message
> > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > > He's talking about multicast IP to multicast MAC translation. Notice
the
> > > MAC address starting with 01
> > >
> > > Patrick
> > >
> > > > Sisqo wrote:
> > > > >
> > > > > Cisco press book (BCMSN) does not really explain well the concept.
> I
> > was
> > > > > wondering if someone can help me break the barrier.
> > > > >
> > > > > Example in the book:
> > > > >
> > > > > 224.163.163.45 = 01-00-5E-23-A3-2D
> > > > >
> > > > > I thought 163=A3, why is the 2nd octet converted to 23?
> > > > >
> > > >
> > > > There is no corelation between MAC address and IP address,
> > > > save for the association you make when you assign an IP to
> > > > an interface.
> > > >
> > > > _________________________________
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