The problem of canonical and non-canonical MAC addresses exists because Token Ring devices start reading each bit of a byte at the most significant bit, while Ethernet devices start reading each bit of a byte at the least significant bit. The 0's and 1's are exactly the same on the Token Ring wire as they are on the Ethernet wire. It is how the Network Interface Cards (NIC) and device drivers read the 0's and 1's that is different. For example, an Ethernet host would see "0100 0000" when reading an unconverted byte sent from a Token Ring host as "0000 0010".
Since we usually look at MAC addresses in Hexadecimal, let's review how to convert the numbers for our purposes. Take a look at the table below. It provides the converted hex digits, and binary examples to show how the numbers were derived: 0=0 (0000 - 0000) 8=1 (1000 - 0001) 1=8 (0001 - 1000) 9=9 (1001 - 1001) 2=4 (0010 - 0100) A=5 (1010 - 0101) 3=C (0011 - 1100) B=D (1011 - 1101) 4=2 (0100 - 0010) C=3 (1100 - 0011) 5=A (0101 - 1010) D=B (1101 - 1011) 6=6 (0110 - 0110) E=7 (1110 - 0111) 7=E (0111 - 1110) F=F (1111 - 1111) When converting from canonical and non-canonical, or the other way around, take the address in one byte (two hexadecimal digits), convert the digits based on this chart or by actually reversing the bits. Once the individual digits are converted, swap them. For example, A7 would become E5, and E5 would become A7. There are several examples in the questions at the end of this chapter. I hope that helps... --- Dennis ----- Original Message ----- From: "Hunt Lee" To: Sent: Monday, May 20, 2002 5:11 PM Subject: CCIE Written Question [7:44578] > I was just wondering if anybody knows a way to translate Ethernet MAC > (Cananical) to Token MAC (non-Cananical) & vice versa?? > > I know how to do the simple ones: > > e.g. 1078.xsxx.yyyy > > Hex Dec Swap Dec Hex > > 10 = 16 => 0001 0000 => 0000 1000 = 8 = 08 > > Or any other ones like > > Dec Hex > 1 01 > 2 02 > 3 03 > 4 04 > 5 05 > 6 06 > 7 07 > 8 08 > 9 09 > 10 0A > 11 0B > 12 0C > 13 0D > 14 0E > 15 0F > 16 10 > 17 11 > 18 12 > 19 13 > 20 14 > 21 15 > 22 16 > 23 17 > 24 18 > 25 19 > > > But I don't know how to do it if they give me a large one e.g. Hex of 78, or > AC etc?? > > Thanks. > > Best Regards, > Hunt Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44581&t=44578 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
