Monday 28 November 2011

What is difference between Limited Broadcast address and Directed Broadcast address

We all know broadcast address . It is the address used to address all in the same LAN ( Local Area network).
In broadcast we have two types : Limited broadcast and Directed broadcast. What is the difference between the directed broadcast and the Limited broadcast ?

Limited broadcast is the broadcast limited to a single LAN and which is to be received by all. It is sent to reserved Class E , IP address The destination MAC address for such frames will be FF:FF:FF:FF:FF:FF.  The router simply drop the Limited broadcast address and does not forward it.

Directed Broadcast address is the local subnet broadcast address. If the subnet is , the directed broadcast address will be , which will be heard by all in the same subnet hosts. The router will receive such packet and process it.The  destination mac address will still be FF:FF:FF:FF:FF:FF, as it is to be received by all hosts.

DHCP packets are Limited broadcast packets and NBNS uses directed broadcast packets.