Lpc2000

Ya correct, probably there was a typo.

Cheers,
Vineet.


Ryan Niemi <ryan@fireserve.net> wrote:     --- In lpc2000@yahoogroups.com, vineet jain <vineetrvce@y...> wrote:
 >
 > Thanks for the input.
 > 
 > Actually there are 2^48 MAC addresses existent in the world.
 > The 1st three octets are assigned by the IEEE. Look up the
 > link for details:
 
 No, the LSB of the first octet must be clear on a valid MAC address. 
 This is the broadcast / group (multicast) bit.  Thus, there are 2^47 -
 1 *valid* MAC addresses (since 00:00:00:00:00:00 is not valid), which
 yields 140737488355327 valid MAC addresses.
 
 > http://anonsvn.ethereal.com/ethereal/trunk/manuf 
 > 
 > After which i feel, the network product the companies sell
 > can configure the last 5 octets. If the production doesn't
 > suffice, they need to buy more first three octets.
 
 A MAC address contains 6 octets, not 8 as you suggest.  The first
 three are assigned by IEEE to a specific manufacturer, and is known as
 the OUI.  Look at the link you provided, which is Ethereal's
 hopelessly outdated copy of the IEEE OUI list, and lists the OUI's
 (first 3 octets) of the manufacturers.  The manufacturer may configure
 the last 3 octets, not 5.  If there were 5 configurable octets, there
 could only be 256 ethernet manufacturers in the world.  Rather, there
 are 3 octets for the OUI, and 3 octets manufacturer-assigned.
 
 Here's the MAC address breakdown:
 
 yy:yy:yy:zz:zz:zz
 
 yy:yy:yy = IEEE-assigned OUI
 zz:zz:zz = Manufacturer-assigned
 
 Additionally, the first octet of the OUI may not have the LSB set. 
 There are 2^23 possible OUI's, and 2^24 possible manufacturer-assigned
 addresses within an OUI.
 
 -Ryan
 
 
 
             

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