Analyzing IP Networks – Answers, Exercise 2

 In 200-301 V1 Ch12: Classful IPv4 Networks, 200-301 V1 Part 4: IPv4 Addressing, CCENT-OLD, IPv4 Ch. 12 Network Analysis

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!

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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 A
2 A
3 C
4 A
5 D N/A N/A

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
5 N/A N/A N/A N/A
Analyzing IP Networks Exercise 2
Analyzing IP Networks Exercise 3
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Good thanks


Better 2nd exercise!


Thanks Len!



I hope all is well.

May I ask why is N/A? The address falls between 0-255.

Thank you

Wendell Odom

Hi Jared,
Thanks! Hope it’s going well with you, too.
The first octet, 229, tells us that the address comes from the class D range of addresses, reserved for multicast purposes. As a result, the class A, B, C rules to find the network ID, etc, do not apply. Those rules only apply in the unicast address range, from first octet 1-126 (class A), 128-191 (class B), and 192-223 (class C).

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