When setting up a home network or troubleshooting internet connection issues, users often need to enter precise network parameters. One of the key elements of TCP/IP configuration is subnet mask, which defines the boundaries of the local segment and allows equipment to route data packets correctly. Without the correct value for this parameter, your device will not be able to "see" the gateway or other devices on the network, even if the Wi-Fi signal itself is excellent.
Many router owners mistakenly believe that accessing this information requires accessing the router's web interface or calling their ISP. In fact, your computer's or smartphone's operating system already contains all the necessary information; it simply needs to be read correctly. In this article, we'll explore all the available methods for obtaining the subnet mask using the gateway IP address and the command line on various platforms.
What is a subnet mask and why is it needed?
A subnet mask is a 32-bit number used in conjunction with an IP address to separate it into two logical parts: the network identifier and the host identifier. Simply put, it tells network equipment which part of the address refers to the "village" itself (the local network) and which refers to a specific "house" (your device). The standard notation is a sequence of four numbers, for example, 255.255.255.0, but in binary form it is a continuous series of ones, alternating with zeros.
Understanding how the mask works is critical when setting up static IP addresses or organizing complex network structures with multiple routers. If you enter an incorrect value, an addressing conflict will occur: the device will think it's on one network, while the gateway will assign it to a completely different one. This will result in complete inaccessibility to local network resources and the internet, despite a formal Wi-Fi connection.
There are two main formats for writing this parameter: decimal (dotted-decimal notation) and prefix (CIDR). In everyday life, we most often encounter the decimal format, where each octad can take a value from 0 to 255. However, in professional environments and modern router interfaces, the slash notation is increasingly common, for example, /24, which is equivalent to the mask 255.255.255.0. Knowing the correspondence between these formats will save you from confusion during configuration.
Defining network settings on Windows
The Windows operating system provides the most comprehensive set of tools for network diagnostics. The fastest way to find out your subnet mask is to use the command line. Press the key combination Win + R, enter cmd and press Enter. In the black window that opens, enter the command ipconfig and press Enter. The system will display a list of all network adapters, and you need to find the section corresponding to your Wi-Fi connection (usually called "Wireless Network" or "Wireless LAN Adapter").
In the command output, you'll see a line labeled "Subnet Mask," which will contain the value you're looking for. Your device's IP address and default gateway (router) will be displayed next to it. Please note that if you have virtual software installed (such as Android emulators or VPN clients), the list of adapters may be long, so use the name of your wireless interface as a guide to avoid confusion.
For those who prefer a graphical interface, there's an alternative. Open "Settings" from the Start menu, go to "Network & Internet," and select "Properties" for your active Wi-Fi connection. Scroll down to the "IP Properties" section, which will list the IPv4 address, default gateway, and subnet mask. This method is less informative, but more intuitive for beginners.
⚠️ Attention: If the subnet mask field displays values other than the default (for example, 255.0.0.0 or 255.255.0.0) on a typical home network, this may indicate a configuration error in the router's DHCP server or manual intervention in the network settings, which requires checking the router's settings.
Viewing network settings on macOS
Apple computer users can access network information through System Preferences. Click the Apple logo in the upper-left corner of the screen and select "System Preferences" (or "System Preferences" in newer versions of macOS). Go to the "Network" section, select your active Wi-Fi connection, and click "More Details" or "Advanced." In the window that opens, click the TCP/IP tab, which will display all the necessary settings, including the subnet mask.
An alternative, faster method for advanced users is to use the Terminal. Launch the Terminal app via Spotlight (Cmd + Space) and enter the command ifconfigUnlike Windows, the output of this command on macOS is more extensive and contains technical information about all interfaces. You need to find the section starting with en1 or en0 (usually it's Wi-Fi), and look for the line netmask.
The mask value in the terminal can be represented in hexadecimal format (for example, 0xffffff00), which corresponds to the standard mask 255.255.255.0. Online calculators or a simple translation can be used for conversion: ff in hexadecimal is equal to 255 in decimal. This output format is typical for Unix-like systems and can sometimes confuse inexperienced users.
How to find your subnet mask on Android and iOS
On mobile devices, detailed network information is often hidden from the user, but modern OS versions do allow this data. On Android, the path may vary depending on the manufacturer's operating system, but the general procedure is as follows: "Settings" → "Wi-Fi" (or "Connections"). Tap the name of your network or the gear icon next to it. In the menu that opens, find the "Advanced" section or scroll down to "View more," which often hides the IP address and subnet mask.
iPhone and iPad owners can also find this information without installing third-party software. Go to "Settings" → "Wi-Fi" and tap the blue information icon (the letter "i" in a circle) to the right of the connected network name. Under "IPv4 Address," you'll see the IP address, subnet mask, and router address. However, iOS often hides the subnet mask if the connection is running in standard DHCP mode, displaying only the IP address and router address.
If you can't see the mask using standard mobile OS tools, you can use specialized network scanning applications, such as Fing or Network AnalyzerThese snails not only display the subnet mask but also allow you to scan the network for connected devices, check speed, and diagnose security issues. This is especially useful when you need to quickly understand the structure of a local network.
☑️ Check network settings
Table of mask and prefix correspondence
When configuring network equipment, you may need to convert a mask from decimal format to CIDR (Classless Interchange Router) format. This is especially relevant when working with VLANs or complex router settings. MikroTik And UbiquitiBelow is a table of the most commonly used masks in home and office networks.
| Prefix (CIDR) | Subnet mask (Decimal) | Binary code | Number of hosts |
|---|---|---|---|
| /8 | 255.0.0.0 | 11111111.00000000.00000000.00000000 | 16 777 214 |
| /16 | 255.255.0.0 | 11111111.11111111.00000000.00000000 | 65 534 |
| /24 | 255.255.255.0 | 11111111.11111111.11111111.00000000 | 254 |
| /30 | 255.255.255.252 | 11111111.11111111.11111111.11111100 | 2 |
The /24 mask is the de facto standard for home networks, as it provides up to 254 unique addresses for devices, more than enough for any residential space. /30 masks are often used by ISPs to set up tunneled connections (such as PPPoE or L2TP), where only two addresses are needed: one for the client and one for the server.
Why can't there be tears in the mask?
In binary notation, a subnet mask always consists of a continuous sequence of ones followed by zeros. A notation like 255.0.255.0 is impossible, as it would violate the logic of separating the network and host, and the equipment would simply refuse to work with such a configuration.
Common connection errors and problems
One of the most common issues is IP address conflicts, which often arise from misunderstanding the subnet mask. If you manually set a static address outside the range defined by your router's subnet mask, the device will not be able to access the internet. For example, if the gateway has an address of 192.168.1.1 with a mask of 255.255.255.0, then your PC's address should be in the range from 192.168.1.2 to 192.168.1.254.
Another error is attempting to use a mask of 255.255.255.255 or 0.0.0.0 in the local interface settings. These values are reserved for special purposes (the broadcast address or default address) and cannot be assigned to a specific network interface for normal operation. The system will usually immediately return an error when attempting to save such settings.
It's also worth mentioning the issue with APIPA addresses. If your computer can't obtain parameters from the router's DHCP server, it assigns itself an address in the 169.254.xx range. In this case, the subnet mask may display as 255.255.0.0, but there will be no internet connection. This is a sure sign that the problem isn't with the mask, but rather with a lack of connection to the router or a malfunction of the router itself.
⚠️ Attention: Router and operating system settings interfaces are regularly updated. The location of menu items or field names may differ depending on the firmware version of your device (e.g., TP-Link Archer or Asus RT). If you don't find an exact match, look for similarly named sections related to LAN, TCP/IP, or local area network.
Additional diagnostic methods
For deep network analysis, you can use command line utilities such as ping And tracert (or traceroute (in Linux/macOS). While they don't directly display the mask, they help you understand whether your device can see other hosts within the intended subnet. If you can ping the gateway but not the neighboring PC, the problem may be a mask mismatch between different devices.
There are also graphical subnet calculators available online. By entering the IP address and the desired number of devices, you can calculate the optimal subnet mask. This is useful when planning a network for an office or smart home, where dozens of devices are connected and careful traffic segmentation is required.
Keep in mind that in modern IPv6 networks, the concept of a subnet mask has been transformed into a "network prefix," which is typically /64 in length. While the principles remain similar, the address length and number of possible combinations have become enormous, virtually eliminating address conflicts in the foreseeable future.
Is it possible to change the subnet mask on a router?
Yes, you can change the subnet mask in the LAN settings section of the router's web interface. However, you should only do this if you fully understand the consequences. Changing the mask will require reconfiguring all static IP addresses on your network and may temporarily disrupt connections to all devices.
What happens if the subnet mask on the PC and router do not match?
The devices will be unable to exchange data correctly. The computer may believe the router is on a different network and attempt to send packets through a non-existent gateway, or the router may ignore requests from the PC, believing they are coming from an untrusted segment.
Does the subnet mask affect internet speed?
The subnet mask itself doesn't affect the physical speed of the link provided by the provider. However, an incorrect setting can lead to increased routing errors and packet retries, which will subjectively make the connection slow and unstable.
Where can I find the gateway IP address if it is not specified?
In Windows, use the command ipconfig In the command line, it will be listed as "Default Gateway." On macOS and Linux, this can be found using the command netstat -nr or ip route accordingly. Typically, this is the first address in the network range (for example, 192.168.0.1).