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How many hosts can be supported by a subnet with a specific mask?

You are given the network 192.168.157.0 with subnet mask 255.255.255.0 to represent your organisation. If it is decided that 3 bits are going to be "borrowed" for subnetting purposes, how many hosts can each subnet have?

need help on this question dont know how to do it

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    dave: your questions keep getting moved to serverfault.com. Why not post them there to begin with? Aug 4, 2009 at 13:47
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    -1 please don't submit homework problems Aug 4, 2009 at 17:16

1 Answer 1

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2 ^ 5 - 2 = 30

You have an 8 bit subnett (the last 0 in the subnett mask) 8 -3 = 5

The -2 is to remove the broadcast and subnett mask addresses

The answer is 30

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  • should that be minus 2? (one for the broadcast and one for the network address?)
    – Dog Ears
    Aug 4, 2009 at 13:47
  • so you mean i will have 5 hosts to each subnet
    – dave s
    Aug 4, 2009 at 13:47
  • or is the network address 0? So it IS 31 as SHiraz has already said.
    – Dog Ears
    Aug 4, 2009 at 13:54
  • Dog Ears was right it should have been -2, have updated Aug 4, 2009 at 14:53
  • @dave: no, the answer is 30. although in practice you might find it's actually 29 as one of those addresses will be needed for the gateway. Aug 4, 2009 at 15:18