An IP m'cast address is 32 bits long (as with any IP address), the first for bits are 0x1110 leaving 28 bits. (Still with me :))
Any m'cast ethernet borne frame has a 48 bit MAC (as do all ethernet frames). A 25 bit prefix is assigned leaving 23 bits. As 28 won't go into 23 there must be some duplication, there is a short fall of five bits and 2 to the 5 is 32. Hence and one m'cast MAC represents 32 IP addresses. For instance 224.1.1.1 224.128.1.1 225.1.1.1 225.128.1.1 etc etc 238.1.1.1 238.128.1.1 239.1.1.1 239.128.1.1 are all allocated a MAC of 0100.5e01.0101. Hope this is explained OK. RB Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=29061&t=29057 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
