# Mistake #2

This is the problem that was randomly generated with my answers:

## IP = 205 . 68 . 198 . 233 / 29

```
Mask = 255 . 255 . 255 . 1 1 1 1 1 0 0 0
Convert 233 to bin:   1 1 1 0 1 0 0 1                            ----------------      Do bit-wise AND:      1 1 1 0 1 0 0 1 (= 232)

Magic = 8
```

## Find the Answers for each

1. `What is the Dotted Decimal Subnet Mask? 255 . 255 . 255 . 248`
2. `Find this SubNetwork 205 . 68 . 198 . 232`
3. `Find the First useable IP address 205 . 68 . 198 . 233`
4. `Find the Broadcast address 205 . 68 . 198 . 239`
5. `Find the Last useable IP address 205 . 68 . 198 . 238`
6. `What is the Total Number of IPs per Subnet? 32 - 29 = 3 ; 23 = 8`
7. `How many useable Hosts Addresses per subnet? 8 - 2 = 6`
8. `What is the Next Subnetwork Number? 205 . 68 . 198 . 240`
9. `What IP Class is this? Class C`
10. `What is the 15th subnetwork number? 205 . 68 . 198 . 112`

As you can see, I got number 10 wrong. The correct answer should have been:

10. 205 . 68 . 198 . 120

### What did I do wrong?

I counted subnetwork number zero as the first subnetwork. Although some networks do use network number zero, for the puposes of subnetting, never count subnetwork zero! Start counting at the next one up. In this case, 205 . 68 . 198 . 8 would have been subnetwork number 1, making
205 . 68 . 198 . 120
subnetwork number 15, not 205 . 68 . 198 . 112.

<-- Back to the main Subnetting page