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Lectures notes for 2010 - KTH

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Broadcasting<br />

• Limited Broadcast<br />

• IP address: 255.255.255.255<br />

• never <strong>for</strong>warded by routers<br />

• What if you are multihomed? (i.e., attached to several networks)<br />

– Most BSD systems just send on first configured interface<br />

– routed and rwhod - determine all interfaces on host and send a copy on each (which is<br />

capable of broadcasting)<br />

• Net-directed Broadcast<br />

• IP address: netid.255.255.255 or net.id.255.255 or net.i.d.255 (depending on the class of<br />

the network)<br />

• routers must <strong>for</strong>ward<br />

• Subnet-Directed Broadcast<br />

• IP address: netid | subnetid | hostID, where hostID = all ones<br />

• All-subnets-directed Broadcast<br />

• IP address: netid | subnetid | hostID, where hostID = all ones and subnetID = all ones<br />

• generally regarded as obsolete!<br />

To send a UDP datagram to a broadcast address set SO_BROADCAST<br />

Maguire Broadcasting 8: 6 of 78<br />

maguire@kth.se <strong>2010</strong>.03.21 Internetworking/Internetteknik

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