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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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migrated from stackoverflow.com Aug 4 '09 at 14:14

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marked as duplicate by Kyle Brandt, Kara Marfia Aug 5 '09 at 13:24

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dave: your questions keep getting moved to serverfault.com. Why not post them there to begin with? –  John Saunders Aug 4 '09 at 13:47
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-1 please don't submit homework problems –  David Mackintosh Aug 4 '09 at 17:16

1 Answer 1

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 '09 at 13:47
    
so you mean i will have 5 hosts to each subnet –  dave s Aug 4 '09 at 13:47
    
or is the network address 0? So it IS 31 as SHiraz has already said. –  Dog Ears Aug 4 '09 at 13:54
    
Dog Ears was right it should have been -2, have updated –  Shiraz Bhaiji Aug 4 '09 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. –  Darth Satan Aug 4 '09 at 15:18