Subnet Calculations - Where Have I Messed Up Here?

[Jay]

I have posted this on another forum as well as here, I have made a bit of a mess with a subnet and for the life of me can't work out how I have done it.


10.0.0.1 --> 10.0.0.64

64 = 0
32 = 0
16 = 0
8 = 0
4 = 0
2 = 0
1 = 1
0 = 0

64 in binary = 01000000 so we need 7 bits or 11111110 (<-- this is my mistake)

1 = 1
1 = 3
1 = 7
1 = 15
1 = 31
1 = 63
1 = 127
0 = 254

so the subnet is 255.255.255.254 but that is not the correct subnet so I have managed to make a mistake along the lines. Can anyone see where I am going wrong?

My error has been found

How it should look

10.0.0.1 --> 10.0.0.64

63 = 1
31 = 1
15 = 1
7 = 1
3 = 1
1 = 1
0 = 0
0 = 0

= 6bit

1 = 1
1 = 3
0 = 6
0 = 12
0 = 24
0 = 48
0 = 96
0 = 192

255.255.255.192

[blueball]

Network on 10.0.0.0

Clients on 10.0.0.1 - 10.0.0.62

Broadcast on 10.0.0.63

Mask 255.255.255.192

[Jay]

10.0.0.0

10.0.0.1 - 10.0.0.62
255.255.255.192
Broadcast on 10.0.0.63

Thanks, I know its .192 but I can't work out how I have made a mess of my calculation

Its my Bit calc that is wrong, now just working back to see why

[blueball]

Thanks, I know its .192 but I can't work out how I have made a mess of my calculation

You did 1 to 64 instead of 0 to 63

[Jay]

You did 1 to 64 instead of 0 to 63

yes I did! nice spot! that 1 digit pushes it over to a 7 bit and makes a right mess of it

63
31
15
7
3
1

6 bit

[blueball]

http://www.subnet-calculator.com/

[oolon]

On a redhat system there is a command called ipcalc.

ipcalc -mn 192.168.2.74/28

Personally I prefer this ip calculator, as you can also download the source, which is all written in perl, and then have it as a stand alone program. Confusingly it is also called ipcalc.

ipcalc 10.0.0.1/26
Address:   10.0.0.1             00001010.00000000.00000000.00 000001
Netmask:   255.255.255.192 = 26 11111111.11111111.11111111.11 000000
Wildcard:  0.0.0.63             00000000.00000000.00000000.00 111111
=>
Network:   10.0.0.0/26          00001010.00000000.00000000.00 000000
HostMin:   10.0.0.1             00001010.00000000.00000000.00 000001
HostMax:   10.0.0.62            00001010.00000000.00000000.00 111110
Broadcast: 10.0.0.63            00001010.00000000.00000000.00 111111
Hosts/Net: 62                    Class A, Private Internet

[Jay]

http://www.subnet-calculator.com/

changed my first post with the way I should have done it. It looks right now.

Thanks