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# CCNA Exam: MAC address #2

Hi,
1) This is related to MAC address at CCNA Exam
2) In one of the prep test:
The question: How is an EUI-64 format interface ID created from a 48-bit MAC address?
The answer: By inserting 0xFFFE between the upper three bytes and the lower three bytes of the MAC address
3) I have 5 of the following questions accordingly:
4) First question: What is EUI-64 format interface ID?
5) 2nd Question: What is 48-bit MAC Address?
6) 3rd question: Waht is 0xFFFE?
7) 4th question: What is "the upper three bytes of the MAC address?" (please provide example)
8) 5th question: What is "the lower three bytes of the MAC address?" (please provide example)
9) Thank you

tjie
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tjie
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3 Solutions

Commented:
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Commented:
ok, here's a standard MAC address, 08:00:0F:63:22:AC. This is written in hexadecimal format to make it easier to read and each pair of numbers represents a byte (4 bits per hex number, 8 bits per byte). If you're having problems with hex wikipedia has a pretty good article for them at http://en.wikipedia.org/wiki/Hexadecimal . Ok, knowing this answers most of the questions such as what is 0xFFFE which his hex for 65534, but you don't need to know that. Think of it as filler for the extra space created by expanding the MAC address. 48 bits is easy, there are 12 hex digits in the MAC address times 4 bits = 48. Again 2 hex digits = 1 byte so upper 3 of example would be 08:00:0F and lower 3 would be 63:22:AC. As for EUI-64 think of it as a 64-bit MAC address, if you want to know details check http://en.wikipedia.org/wiki/EUI-64
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Commented:
oh and the resultant MC address would be 08:00:0F:FF:FE:63:22:AC
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