# subnet masking related confusion [duplicate]

I am new to subnet masking. I have a question. If network address is 10.10.10.0/23, what will be the first and last usable IP address of this network?

I don't believe that 10.10.10.10/23 is a network address, it would be a host address on a network; the network address would be 10.10.10.0, the subnet mask would be 255.255.254.0.

Regarding the calculations: I always convert to binary - 10.10.10.10 is

``````00001010 00001010 00001010 00001010
``````

With a 23 bit subnet mask, that's

``````11111111 11111111 11111110 00000000
``````

``````11111111 11111111 11111110 00000000
00001010 00001010 00001010 00001010
``````

the network address is the part below the 1's, followed by zeros:

``````00001010 00001010 00001010 00000000
``````

which is 10.10.10.0

The hosts are determined by the rest of the bits. Since the mask is 23 bits, there are 9 bits for the host portion of the addresses. (32-23=9)

so they range from

``````00000000 00000000 00000000 00000001
``````

to

``````00000000 00000000 00000001 11111111
``````

`````` 00001010 00001010 00001010 00000000
+00000000 00000000 00000000 00000001
____________________________________
00001010 00001010 00001010 00000001
``````

which is 10.10.10.1 - the high value:

`````` 00001010 00001010 00001010 00000000
+00000000 00000000 00000001 11111111
____________________________________
00001010 00001010 00001011 11111111
``````