subnetting question

samxd

i would like to know if someone can explain why it seems odd for this to happen below :



150.5.0.0 -->100 Networks

150.5.0.0 - 150.5.1.255

150.5.2.0 -155.5.3.255

150.5.4.0 -155.5.5.255

...

---

170.50.0.0 --> 1000 Networks

170.50.0.0 – 170.50.0.63

170.50.0.64 – 170.50.0.127

170.50.0.128 – 170.50.0.191

170.50.0.192 – 170.50.0.255

170.50.1.0 – 170.50.1.63

...

question: in the first example they started incrementing in the 3rd bit while in the second they incremented using the last bit. Why was this if they are both class B?

hypnotoad

In part 2, since the block size of IP addresses increments by 64, you know there are 2^6 bits being used for the host portion.

NNNNNNNN.NNNNNNNN.SSSSSSSS.SSHHHHHH

This gives the Network bits (16 of them), then 10 Subnetwork bits, then 6 left over for IP ranges. This means the IP ranges must be from 0-64. They can't be anything else. So instead of counting by 256, the default, the subnet masks dictates that the blocks will be counted by 64.