Monitoring the devices connected to a local area network (LAN) is a fundamental task for troubleshooting connectivity, ensuring network security, and managing shared resources. While graphical user interfaces and third-party scanners offer convenience, the Windows Command Prompt (CMD) remains one of the most powerful and immediate tools for network discovery.

To see all devices on your network quickly using the Command Prompt, you can use the arp -a command. This command displays the Address Resolution Protocol (ARP) table, which lists the IP and MAC addresses of all devices your computer has recently communicated with.

However, the arp -a command has limitations. It only shows active or recently active devices that have exchanged data with your system. To perform a more comprehensive scan and "wake up" all devices on the subnet, more advanced techniques involving ping sweeps and PowerShell scripts are required.

Viewing the ARP Table with the Command Prompt

The Address Resolution Protocol (ARP) is the bridge between a logical IP address and a physical MAC address. When your computer wants to send data to another device on the same network, it needs to know that device’s hardware address. The ARP table is a local cache of these mappings.

How to Run the Basic ARP Command

  1. Press the Windows Key + R on your keyboard to open the Run dialog box.
  2. Type cmd and press Enter to launch the Command Prompt.
  3. In the black terminal window, type the following command and press Enter: arp -a

Understanding the Output

Once the command executes, you will see a list organized under three columns:

  • Internet Address: The IP address of the connected device (e.g., 192.168.1.5).
  • Physical Address: The MAC (Media Access Control) address, a unique hardware identifier for the device's network card.
  • Type: Usually labeled as "Dynamic" or "Static." Dynamic addresses are assigned by your router via DHCP, while static addresses are manually assigned.

One detail to notice is the Interface line at the top of each block. If your computer has multiple network adapters—such as a physical Ethernet port, a Wi-Fi card, and a virtual VPN adapter—the ARP table will be separated by these interfaces. You should look for the interface corresponding to your local network IP range (typically starting with 192.168.x.x or 10.x.x.x).

Why the Basic ARP Command Might Miss Devices

A common frustration for users is running arp -a and seeing only two or three entries when they know there are dozens of smart light bulbs, phones, and laptops on the network. This happens because the ARP cache is passive.

If your laptop has not sent a "handshake" or data packet to your smart TV in the last few minutes, the router or the TV itself may have timed out of your computer's local ARP table. To fix this, you need to force your computer to reach out to every possible IP address in your network range. This process is known as a "Ping Sweep."

Performing a Network-Wide Ping Sweep Using Command Prompt

By combining a simple loop with the ping command, you can force every device on your subnet to respond, thereby populating your ARP table with fresh data.

The Command for a 24-bit Subnet

Most home networks use a subnet mask of 255.255.255.0, meaning the first three sets of numbers in your IP address stay the same (e.g., 192.168.1.x), and the last number ranges from 1 to 254.

To scan this entire range, copy and paste the following command into your Command Prompt:

for /l %i in (1,1,254) do @ping -n 1 -w 100 192.168.1.%i | find "Reply"

Note: Replace 192.168.1 with the first three octets of your own network’s IP address.

Breakdown of the Loop Command

  • for /l %i in (1,1,254): This tells CMD to start at 1, increment by 1, and end at 254.
  • do @ping -n 1: This instructs the system to send exactly one ping packet to each address.
  • -w 100: This sets the timeout to 100 milliseconds. This makes the scan much faster than the default 4-second wait time.
  • | find "Reply": This filters the output so that the screen only displays addresses that actually respond, hiding the "Request timed out" messages for empty slots.

After this loop finishes (which may take about 30–60 seconds), run arp -a again. You will notice the list is significantly longer and more accurate.

Using PowerShell for Faster and More Detailed Discovery

Windows PowerShell is a more robust environment than the traditional Command Prompt. It handles network objects more efficiently and can provide cleaner output.

The PowerShell Ping Script

If you are using Windows 10 or 11, you can right-click the Start button and select Windows PowerShell or Terminal. Enter the following script: