Usable IP addresses are separated in 3 classes: class A, B and C. As we previously discussed, class A addresses are the ones from to, class B is from to and class C are those IP addresses in the range of to To help you easily understand this topic, we will use an example IP address from each class.

Finding the network, broadcast and host address on a class A IP address.

A class A IP address is an IP within the range of to We will use the IP in this example. This IP address, not only it belongs to class A, but it also belongs to the private IP space, used for internal networks. The default subnet mask for a class A address is This means, our network is from to

Previously, we told you that the first IP address on a network is the network address. In the networking world, we use this address to refer to the whole network. The network address in our case is

We also told you that the broadcast address, the address used for a host to send packets in the whole network, is the last address. Yes, that’s correct, the broadcast address in our case is

Any address between the network and the broadcast address is a usable address for your network hosts, meaning that you can have up to 16,777,214 hosts in your network (2^24 – 2).

Finding the network, broadcast and host address on a class B IP address.

This time, we will use the IP address. As you can see, this is a valid class B address, and it’s a public one. The default subnet mask for a class B address is We get the range from to for our network. As you may have already guessed, the network address is and the broadcast address is The remaining addresses are used by the hosts of the network, but the network can have no more than 65,534 (2^16 – 2) hosts.

Finding the network, broadcast and host address on a class C IP address.

Similar to the other examples, we take a class C address: The default netmask in class C is meaning that we’ll get the network within the range of to The network address is and the broadcast address is We can have up to 254 hosts in our network.

The subnet mask is the component in IP addressing that separates networks. When you assign an IP address to a device, you must assign a network mask too. If you’re not assigning the correct subnet mask, you will end up with no connectivity between that host and the others. The bits set to 1 in the subnet mask denotes that those bits in the IP address cannot change. Comparing these bits allows devices in the network to know which network they belong to.

Routers are making an ANDing operation to find out the network address. ANDing is a basic binary operation. In this process, they compare the IP address bits with the subnet mask bits. If the bits are set to 1, the result of the ANDing operation will be 1. If they are both 0 or any combination of 1 with 0, the result is 0. Let’s use an example to better describe this. We will use the IP address with the netmask to determine the network address.

IP address:       192      .        0        .         0       .      1
11000000   00000000   00000000   00000001
Netmask:         255      .      255     .        0        .     0
11111111   11111111   00000000   00000000

Network:     11000000   00000000   00000000   00000000
192      .       0        .        0         .      0

We hope you found this topic about IP addresses helpful in your preparation for the CCNA exam. In our next topic, we will study the subneting process. This will help you work with Variable Length Subnet Masking (VLSM) and  Classless Inter-Domain Routing (CIDR) and it’s a very important topic in your preparation for Cisco’s CCNA exam.