Subnet calculation

  • Subnet, network and broadcast addresses can be easily computed with the IP calculator, ipcalc
    Example, 128.6.34.55/27 
    
#ipcalc 128.6.34.55/27

Address:   128.6.34.55          10000000.00000110.00100010.001 10111
Netmask:   255.255.255.224 = 27 11111111.11111111.11111111.111 00000
Wildcard:  0.0.0.31             00000000.00000000.00000000.000 11111
=>
Network:   128.6.34.32/27       10000000.00000110.00100010.001 00000
HostMin:   128.6.34.33          10000000.00000110.00100010.001 00001
HostMax:   128.6.34.62          10000000.00000110.00100010.001 11110
Broadcast: 128.6.34.63          10000000.00000110.00100010.001 11111
Hosts/Net: 30                    Class B

  • The smallest IP on a network is usually reserved for a gateway.
  • Hosts on the different networks (subnets), communicate through gateways.
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