# Analyzing IP Networks – Answers, Exercise 1

Today’s post lists the answers to the previous post’s question, with a few comments, with a place to discuss. Nothing snazzy, but it does hit the fundamentals. Enjoy!

## Class, Network ID, and Network Broadcast

The Network ID can be derived from the class A, B, or C DDN value by copying the network octets, and writing a 0 for the rest of the octets. Similarly, the network broadcast address can be found by using the same logic, but writing a 255 instead of 0 for the host octets. Table 2 shows the class for each of the five problems, along with the derived network ID and network broadcast address for each class A, B, or C address.

#### Table 2: Network IDs and Network Broadcast Addresses

 DDN Value Class Network ID Network Broadcast Address 1 100.100.100.100 A 100.0.0.0 100.255.255.255 2 200.200.200.200 C 200.200.200.0 200.200.200.255 3 300.300.300.300 None N/A N/A 4 128.128.128.128 B 128.128.0.0 128.128.255.255 5 191.191.191.191 B 191.191.0.0 191.191.255.255

## Usable Host IP Addresses

To find the range of IP addresses that can be used by hosts in the (unsubnetted) classful network, just add 1 to the network ID and subtract 1 from the network broadcast address. Table 3 shows the results for these five problems.

#### Table 3: Ranges of Usable Addresses

 Network ID Lowest Usable Host Address Highest Usable Host Address Network Broadcast Address 1 100.0.0.0 100.0.0.1 100.255.255.254 100.255.255.255 2 200.200.200.0 200.200.200.1 200.200.200.254 200.200.200.255 3 N/A N/A N/A N/A 4 128.128.0.0 128.128.0.1 128.128.255.254 128.128.255.255 5 191.191.0.0 191.191.0.1 191.191.255.254 191.191.255.255
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## 1 Comment

1. Len October 17, 18:03

good first exercise!

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