MSG Re-posted > -----Original Message----- > From: Thompson, Robert D > Sent: 12 December 2001 08:10 > To: [EMAIL PROTECTED] > Cc: '[EMAIL PROTECTED]' > Subject: RE: CCNP Switching - Mapping MAC address to IP Multicast > [7:10] > > HI Sergio, > > The best way I can explain this is in the following way.... > > > Remember to convert the IP address given to binary. The reason for this is > to convert binary to hex (you need to know how to convert binary to hex, > thats the key here) > > Example (first convert to binary) > > 147.184.9.9 = 10010011.10111000.00001001.00001001 > > now convert to Hex, but only the 23 bits (on of the rules) , starting from > the right, and forget the rest (as you need to pre-pend 01 00 5E to your > answer, also an IANA rule...) > > 10010011.10111000.00001001.00001001 > > Do Not > Convert Convert > > = in binary > > 0111000.00001001.000010001 > > now convert to hex > > = in hex using 8421 code to get hex (break binary groups up into groups of > 4, then convert to hex) > > = 0111000 = 38 in hex ---- > =00001001 = 09 in hex (or 9) ------------ 0111000.00001001.00001001 > =00001001 = 09 in hex (or 9) ---- > = 38.09.09 > > = with pre-pend of 01.00.5E > =01.00.5E.38.09.09 (this answer is your hex answer for ip address > 147.184.9.9 mapped to multicast mac address) > > > > This is in your notes on CCNP switching....(below is a snip taken from > cisco web site) > > > Ethernet MAC Address Mapping > The IANA owns a block of Ethernet MAC addresses that start with 01:00:5E > in hexadecimal format. Half of this block is allocated for multicast > addresses. The range from 0100.5e00.0000 through 0100.5e7f.ffff is the > available range of Ethernet MAC addresses for IP multicast. > This allocation allows for 23 bits in the Ethernet address to correspond > to the IP multicast group address. The mapping places the lower 23 bits of > the IP multicast group address into these available 23 bits in the > Ethernet address. > HTH > > Regards > > Rob > > NA, NP > > -----Original Message----- > From: Sergio [SMTP:[EMAIL PROTECTED]] > Sent: 11 December 2001 20:33 > To: [EMAIL PROTECTED] > Subject: CCNP Switching - Mapping MAC address to IP Multicast [7:10] > > Hi all. This is my first message here. Greetings from Spain ;) > > Now, i have a question for you. I'm preparing my CCNP Switching exam, and > now > im reading about IP Multicast. > > The book says that IANA reserved some MAC address for using with IP > Multicast. > The book also says that MAC addresses must be mapped to IP Multicast > address, > and it explains how to map them. But i cant understand it. I dont > understand > how to map MAC address to IP Multicast addresses. > > Can u help me? > > Thanks in advice.
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