Appendix E. Broadcasts in Switched LAN Networks

To communicate with all or part of the network, protocols use broadcast and multicast datagrams at Layer 2 of the Open Systems Interconnection (OSI) model. This obviously supposes a medium that supports broadcasting (such as Ethernet, for instance). When a node needs to communicate with every station of the network, it sends a datagram to the MAC address FF-FF-FF-FF-FF-FF (a broadcast), which is an address to which the network interface card (NIC) of every host must listen to. Routers, operating at Layer 3 of the OSI model, typically do not forward such broadcasts. They limit them to the segment they originated from. When a host needs to communicate with part of the network, it sends a datagram to ...

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