Always a good day to talk about L2 Multicast Address.
A Josinfo #ccieofpeople reflection.
Since remote times, an device can only communicate on the network after have L2 frame with NIC Burn-in Address MAC (source and destination) respective address.
In a multicast network environment we also need a MAC address, to determine an group of devices that need talk, different of traditional MAC Burn address of NIC, the multicast address are attach dynamically.
Each service or instruction have your kind of multicast address, also need a L2 Mac-Address. I was defined around 1990 by IANA one OUI that its registered on high-order as 01-00-5E, and designated to engineer to adequate only half of this OUI to suitable a combination of IP address on a half portion of OUI.
00000001:00000000:01011110:0|0000000:00000000:00000000 (01:00:5E:00:00:00)
00000001:00000000:01011110:0|1111111:11111111:11111111 (01:00:5E:7F:FF:FF)
Within these two ranges, the MAC address has the first 25 bits in common, and the remaining 23 bits are available to map the 23 Bits against 28 IP Multicast Group.
As 32 bits (IP Datagram) left 28 bits for Multicast ID addressing and if mapping with the remaining 23 bits (Mac Address Datagram) of the Low Order MAC address left to be used for mapping the Multicast group on the Ethernet network, we will have this way an overlap of 5 bits, if we raise 2^5 = 32, then we will have an overlap of 32 addresses that will be represented through a single MAC address 32 to 1
By
#multicast #cciepower #pim #cisco #ull #hft #exchanges #brokerage #trading #josinfo #nac #ise #ciscoise #nasdaq #nyse #network
