networking - Is a subnet's broadcast address required to be the highest address in the subnet? -

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for example, consider following network:

ip address: 192.168.0.1 subnet mask: 255.255.255.0

is broadcast address required 192.168.0.255?

broadcast address defined rfc 919

yes, required. (direct) broadcast address "all-ones-address" in local network defined rfc 919, last address in network range.

since local network layer can map ip address data link layer address, choice of ip "broadcast host number" arbitrary. simplicity, should 1 not assigned real host. number bits ones has property; [...]

examples

for network example, 192.168.0.255, expressed in binary:

11000000 10101000 00000000 11111111

for network 10.0.0.32/248 (thus subnet mask 255.255.255.248), 10.0.0.39 (next subnet starts @ 10.0.0.40).

00001010 00000000 00000000 00100111

exemptions

exemptions exist /31 , /32 networks. /31 networks (p2p-networks) not have broadcast address, have 2 hosts , used connect networks. /32 networks reference single host dedicated routing rules (as there no gateway).


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