hi all, this may seem a very stupid question but i just cant do it. I was reading Unicast-Prefix-Based Multicast Addresses and under that i am confused on how to calculate plen ? this is the example given in cisco press deploying ipv6.
Unicast Prefix: 2001:100:abc:1::/64
Unicast Prefix Scope Global: E
Choose Group ID: 11FF:11EE
Resulting Multicast Address: FF3E:0040:2001:100:abc:1:11FF:11EE
how plen was calculated to be 40 bits ? can someone help me or am i misinterperating the result ?