IP Addresses and Subnet Masks

Date Updated: September 26, 2019 FAQ #5894
Question:
IP Addresses and Subnet Masks
Answer:

IP Addresses and Subnets can be confusing at times, especially when using IP Address ranges which are less common. This guide will help you understand how IP Addresses and Subnet Masks work. This guide only discusses IPv4 addresses. Shure devices do not support IPv6 at this time.

What is an IP Address?

An IP Address is a unique address for a device which sends and receives network traffic on a network. Some devices may have more than one IP Address, because they have multiple internal components which need to communicate, or because they need to operate on multiple networks at the same time.

An IP Address consists of four numbers called octets that are separated by periods. Each number can range from 0 to 255. An example of an IP Address is: 192.168.1.20.

There are four very common ranges of IP addresses which are used for private networks. These addresses cannot be accessed over the Internet, and so are suitable for AV networks. If you are not sure what range of addresses to use, you should use one of these:

  • 192.168.0.0 to 192.168.255.255 (65,536 possible IP addresses)
  • 172.16.0.0 to 172.31.0.0 (1,048,576 possible IP addresses)
  • 10.0.0.0 to 10.255.255.255 (16,777,216 possible IP addresses)
  • 169.254.0.0 to 169.254.255.255* (65,536 possible IP addresses)

* The last range, 169.254.x.x, is a special IP address range that is reserved for devices to self-assign an address. You generally do not manually assign addresses in this range.

There are some additional IP Addresses and ranges of IP Addresses you should be aware of:

  • 0.0.0.0: No IP Address. This is sometimes entered in the Gateway field when you want a network to be isolated. See the section on Subnets and Gateways below.
  • 127.0.0.1 (and 127.0.0.0-127.255.255.255): This address always sends data back to the device that sent it. It's sometimes called localhost or a loopback address. Do not ever assign an address beginning with 127 to a device.
  • 224.0.0.0-239.255.255.255: These are Multicast IP Addresses. See Multicast and IGMP In Depth for more information on Multicast IP traffic.
  • Any other address range not mentioned: other IP addresses should be assumed to be part of an enterprise network which is connected to the public Internet. Do not use those addresses unless your IT department directs you to do so.

Subnet Masks and Gateways

A Subnet Mask defines which range of IP Addresses are within a local network, and which ones are not. Subnet masks always work from left to right. Devices are said to be within the same subnet if their IP Address starts with the same digits, but ends with a different set of digits.

Sometimes, it's easy to tell which part of an IP address is part of the local network and which is not (when the subnet mask consists only sections that are 255 and 0), but sometimes it may not be as clear.

Example IP Address 192.168.1.20
Subnet Mask 255.255.255.0
Starting Address in Subnet 192.168.1.0
Ending Address in Subnet 192.168.1.255
   
Example IP Address 192.168.1.20
Subnet Mask 255.255.0.0
Starting Address in Subnet 192.168.0.0
Ending Address in Subnet 192.168.255.255
   
Example IP Address 192.168.1.20
Subnet Mask 255.0.0.0
Starting Address in Subnet 192.0.0.0
Ending Address in Subnet 192.255.255.255

If the subnet mask is 255.255.255.0, then the first three octets of all devices must be the same. The 4th octet must be different and unique. A maximum of 254 devices can be used in this subnet.

If the subnet mask is 255.255.0.0, then the first two octets of all devices must be the same. The combination of the last two octets must be different and unique. 65,534 devices can be used in this subnet.

The very first address and very last address in a subnet are specially reserved addresses and cannot be assigned to devices. Devices that are within the same subnet will be able to communicate with one another, but a gateway is required to communicate with devices in different subnets. When traffic is intended for a device outside of the subnet, it is sent to the gateway to be routed to the correct destination. The gateway then sends the response back to the device that originally sent the request.