# Subnet Masks - Spring 2008 - March 5th

1. What are the only 9 decimal numbers that can ever be in a Subnet Mask?

Why is it very useful to be able to know that 255 - 0, 255 - 1, 255 - 3, 255 - 7, 255 - 15, 255 - 31, 255 - 63, 255 - 127 and 255 - 255 are those 9 numbers.
What do all of the above numbers have in common when you write them in binary? Especially 254, 252, 248, 240, 224, 192 and 128 seen in binary!

What do 1, 3, 7, 15, 31, 63, and 127 all have in common?

2. Subnet Masks from late 1990s when UNI had 255.255.252.0 as the subnet mask.
```If the subnet mask is 255.255.252.0 the in binary, each octet expands
and the subnect mask looks like this:

255.255.252.0  is  11111111.11111111.11111100.00000000
******** ******** ------
```
3. Subnet Masks further reading from 2006 is very helpful on having more than 300 or 800 subnets are your network and what SUBNET MASK would be used.

4. VIP QUIZ: Subnet Masks QUIZ - take home quiz DUE ON FRIDAY, March 7th, 2008.

5. Subnet Masks - Group Exercise.

6. Subnet Masks - 255.255.224.0 example.

7. Subnet Masks - questions and answers about what subnet mask to use. Feb 6th, 2007.

8. Subnet Masks - Excel Spreadsheet display of concept. Feb 6th, 2007.

9. Subnet Masks - another Excel spreadsheet look at network 191.202.0.0 with subnet mask 255.255.224.0 and result of masking various IP numbers. Feb 6th, 2007.

10. Subnet Masks one more time. Feb 7th, 2007.

11. Subnet Masks - Hamming codeword and MiddleEarth.com exercise.