Topic: Multicast
r1 is a multicast router. It receives a packet with the destination address of 224.255.1.10. What will it do with this packet?
Yesterday’s Question
Question Of The Day: 23 May, 2008
Topic: Multicast
What is the MAC Address of 242.9.169.28?
Answer: 01:00:5e:09:a9:1c
Let’s start by converting the multicast IP address to binary:
242 11110010
9 00001001
169 10101001
28 00011100
So we have:
11110010 00001001 10101001 00011100
Multicast addresses use a base MAC Address of 01:00:5e:xx:xx:xx with the 25th bit always set to 0:
00000001 00000000 01011110 000000000 00000000 00000000
To form the Multicast MAC Address we just need to take the 23 lower order bits of the multicast IP address and replace the 23 lower order bits in the base multicast MAC address:
11110010 00001001 10101001 00011100
00000001 00000000 01011110 00000000 00000000 00000000
00000001 00000000 01011110 00001001 10101001 00011100
Converting that back to hexadecimal, we get our answer:
01:00:5e:09:a9:1c
