ISRO Computer Science (CSE) 2014 - Question 71

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Which of the following is not a valid multicast MAC address?

  • A. 01 : 00 : 5E : 00 : 00 : 00
  • B. 01 : 00 : 5E : 00 : 00 : FF
  • C. 01 : 00 : 5E : 00 : FF : FF
  • D. 01 : 00 : 5E : FF : FF : FF

Answer: D. 01 : 00 : 5E : FF : FF : FF

Explanation: Wait, standard Multicast MAC range: 01-00-5E-00-00-00 to 01-00-5E-7F-FF-FF. \nThe 25th bit must be 0.\n(d) has FF in 4th byte. 0xFF = 11111111. 25th bit is 1? \nRange check: \n(a) ...00 00 00 (Valid)\n(b) ...00 00 FF (Valid)\n(c) ...00 FF FF (Valid)\n(d) ...FF FF FF. 4th byte FF > 7F. Invalid.

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