--- title: "CallTower Information - IP Addressing/Subnet" slug: "calltower-information-ip-addressing-subnet" tags: ["calltower", "public"] updated: 2026-07-27T14:08:34Z published: 2026-07-27T14:08:34Z canonical: "learn.calltower.com/calltower-information-ip-addressing-subnet" stale: true --- > ## Documentation Index > Fetch the complete documentation index at: https://learn.calltower.com/llms.txt > Use this file to discover all available pages before exploring further. # CallTower Information - IP Addressing/Subnet ## IP Addressing: ### *Overview:* This document will go over the fundamentals of what an IP Address is and does. This study document should help the reader understand how IP addresses and subnets are used. ### *What is an IP address?* - An unique identifier given to a computer or device (host) for a TCP/IP network. - A 32-bit binary number usually represented as 4 decimal numbers separated by a period Example: 206.40.185.73 Address in Binary: 11001110.00101000.10111001.01001001 #### Bits and Bytes: IP address: 206.40.185.73 11001110.00101000.10111001.01001001 - A bit – A single 1 or 0. Positive or Negative, Light or No Light Example: 11001110 - A byte – 8 Bits. There are 4 bytes in a IPv4 Address. Example: 11001110.00101000.10111001.01001001 Octet = 1 Byte Each bit represents a numerical value: 10000010. 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 What numerical value do the following numbers represent? 00000101 11000000 Each address is 32 bits wide Valid addresses can range from 0.0.0.0 to 255.255.255.255 WHY? #### *Network and Host Addresses* - Each address consists of two parts 1. The network address 2. The host address The Network Address is considered the Subnet The host address is the IP assigned to the end point device Which part belongs to the network and which part belongs to the node? Class A – XXXXXXXX.yyyyyyyy.yyyyyyyy.yyyyyyyy Class B – XXXXXXXX.XXXXXXXX.yyyyyyyy.yyyyyyyy Class C – XXXXXXXX.XXXXXXXX.XXXXXXXX.yyyyyyyy X = Network Y = node #### *The Five Network Classes* 1. Class A – binary begins with 0 - 00000001 (110) to 01111111 (12610) - 16,777,214 Hosts 2. Class B – binary begins with 10 - 10000000 (12810) to 10111111 (19110) - 65,534 Hosts 3. Class C – binary begins with 110 - 11000000 (19210) to 11011111 (22310) - 254 Hosts 4. Class D – binary begins with 1110 - 22410 to 23910 - Reserved for multicasting 5. Class E – binary begins with 1111 - 24010 to 25410 - Reserved for future use There are three IP network addresses reserved for private networks 1. 10.0.0.0/8 2. 172.16.0.0/12 – 172.31.255.255 3. 192.168.0.0/16 These can be used by anyone setting up an internal/home/office network. Routers will never forward packets coming from these addresses out to the internet. The internet does not recognize these as public IP’s ### *Subnetting* - …can be done for a variety of reasons - Organization - Use of different physical media - Preservation of address space - Security - The most common reason is to control network traffic - In an Ethernet network, all nodes on a segment see all packets transmitted by other nodes on that segment – collision domain - Performance can be adversely affected under heavy traffic loads - A router is used to connect IP networks to minimize the amount of traffic each segment must receive – Broadcast Domain ***Subnet Masking:*** - Applying a subnet mask allows you to identify the network and node parts of the address. A router will then determine whether the address is local or remote. - Network bits are masked as 1s - Node bits are masked as 0s - Class A – 255.0.0.0 - 11111111.00000000.00000000.00000000 - Class B – 255.255.0.0 - 11111111.11111111.00000000.00000000 - Class C – 255.255.255.0 - 11111111.11111111.11111111.00000000 Applying a subnet mask allows you to identify the network and node parts of the address. A router will then determine whether the address is local or remote. 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 What are the masks below? 11111111.11111111.11111111.00000000 11111111.11111111.11111110.00000000 11111111.111111111.00000000.00000000 11111111.111111111.11111111.11000000 To find the subnet mask on a windows machine: This is where it is located: [![Picture1.png](https://cdn.us.document360.io/4662144b-ab1f-4796-8b7b-e9f9c609894f/Images/Documentation/Picture1(1).png?sv=2026-02-06&spr=https&st=2026-11-04T22%3A52%3A40Z&se=2026-11-04T23%3A52%3A40Z&sr=c&sp=r&sig=ch%2BN16FD%2BoHiSeGMj7qzWZ3iT2rJUryBtJXQijdpHTE%3D)](https://cdn.us.document360.io/4662144b-ab1f-4796-8b7b-e9f9c609894f/Images/Documentation/Picture1(2).png?sv=2026-02-06&spr=https&st=2026-11-04T22%3A52%3A40Z&se=2026-11-04T23%3A52%3A40Z&sr=c&sp=r&sig=ch%2BN16FD%2BoHiSeGMj7qzWZ3iT2rJUryBtJXQijdpHTE%3D) #### Determining Hosts/Network ID/Broadcast Address: First IP of the subnet is not used. It is the network ID. Last IP of the subnet is not used it is the broadcast address. All devices on the same physical segment share a common network ID (subnet mask) How many hosts are available? 255.255.255.0 255.255.255.128 255.255.254.0 The first Host IP of the available hosts is usually configured as the default gateway. That is an industry standard but the default gateway can be configured as any host IP address on the subnet. An Internet Protocol (IP) Address is a unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.