I am having trrouble wrapping my head around this certain form of cidr notation...

with this info:

Network = 192.168.1.128 (last byte = 1000 0000)
Netmask = 255.255.255.192 (last byte = 1100 0000)
First address: 192.168.1.128 (including network)
Last address: 192.168.1.191 (including broadcast)

How can the address range be represented by:

192.168.1.128/26

I can't seem to make since of this in my head... I fully understand the concepts behind this network and all it entails but don't seem to follow this form of notation. What is it telling me?

ok...

looks to me like this notation is telling me that the hosts within this network range from:

192 168 1 128
1100 0000 1010 1000 0000 0001 1000 0000

to

192 168 1 191
1100 0000 1010 1000 0000 0001 1011 1111

all three together:

1100 0000 1010 1000 0000 0001 1000 0000
1100 0000 1010 1000 0000 0001 1011 1111
1111 1111 1111 1111 1111 1111 1100 0000

yields the address range resulting in a bitmask of 26 bits...



Weeeeeeeeeeeeeeeeeee!!!!

edit: which one could gather from the netmask...

Correct. The network is derived by from the IP address by ANDing it with the subnet mask -

192.168.1.128
AND
255.255.255.192 (/26)

or

11000000 10101000 00000001 10000000
AND
11111111 11111111 11111111 11000000
=
11000000 10101000 00000001 10000000 or 192.168.1.128



Do the same with 192.168.1.191 -

11000000 10101000 00000001 10111111
AND
11111111 11111111 11111111 11000000
=
11000000 10101000 00000001 10000000 or 192.168.1.128

See, same network! Try the same thing with 192.168.1.192 and you'll see that the resultant network is different.

wow, that makes sense.... i've always been ropey with that... so i just always pretended it didn't exist!

Hey, a million ostrich's can't be wrong!