IPv4 GLOP multicast addresses

GLOP multicast address block reservation is 233.0.0.0/8. GLOP multicast address block reservation for providing any organization with their own registered 16-bit public AS number with their own globally unique multicast IP address range. So, there must be a mapping with Autonomous System number and IPv4 multicast addresses. The word GLOP is not an abbreviation for anything, GLOP is just GLOP.

16-bit Autonomous System Numbers (ASNs) are mapped with IPv4 Class D multicast addresses as explained below. Two middle octets of GLOP multicast address block are derived from assigned 16-bit Autonomous System Numbers (ASN). Please note that this method of generating multicast addresses based on Autonomous System numbers is not applicable to 32-bit Autonomous System Numbers.

Examples of generating GLOP addresses

Example 1

Lets consider an example of a 16-bit Autonomous System Numbers (ASN) of 5670. The binary equivalent of 5670 is ‭1011000100110‬

1. Let us pad the binary equivalent of 5670 in left-side with three bits to make it 16 bits. This makes no change in its value. That is, ‭0001011000100110‬.
2. lets split the ‬‭binary equivalent of 5670 (0001011000100110‬ ) into two 8-bit parts, 00010110 and 00100110.
3. Convert each 8-bit part into decimal. The decimal equivalent of 00010110 is 22 and 00100110 is 38.
4. GLOP multicast address block for Autonomous System Number (ASN) 64515 is then 233.22.38/24.

Example 2

Let’s consider another example of a 16-bit Autonomous System Numbers (ASN) of ‭64515‬. The binary equivalent of ‭64515 is ‭1111110000000011.

1. lets split the ‬‭binary equivalent of ‭64515 (‭1111110000000011) into two 8-bit parts, 11111100 and 00000011.
2. Convert each 8-bit part into decimal. The decimal equivalent of 11111100 is 252 and 00000011 is 3.
3. GLOP multicast address block for Autonomous System Number (ASN) 64515 is then 233.252.3/24.