Question

Assume that you have the following MAC address 01:00:5e:XX:XX:XX (where the last 3 bytes matches the last 3 bytes of your own device MAC address), figure out what IPv4 multicast address does this MAC address belongs to?

Answer 1

Solution

Lets start with this MAC address

01:00:5e:0b:01:02

First step is to translate the MAC address from hex to binary

0	1	0	0	5	e	0	b	0	1	0	2
0000	0001	0000	0000	0101	1110	0000	1011	0000	0001	0000	0010

The above table shows that how we have translated the hex to binary the full MAC address is

0000 0001

0000 0000

0101 1110

0000 1011

0000 0001

0000 0010

Lets take the lowest 23-bits of the MAC address

0000 0001

0000 0000

0101 1110

0000 1011

0000 0001

0000 0010

The highlighted bits are the lowest 23-bit of the MAC address

Next step is to take class D multicast IP address in binary

1110 0000

0000 0000

0000 0000

0000 0000

1110 is the class D ip address that is mentioned in binary in decimal it is 224

The 00000 are the 5 bits we are losing the reason is we need to map 28-bit unique multicast IP address to 23-bit multicast MAC address

1110 0000

0000 1011

0000 0001

0000 0010

Now convert this binary to decimal

224	11	1	2
1110 0000	0000 1011	0000 0001	0000 0010

Therefore complete multicast IP address for MAC is

224.11.1.2

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all the best