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arp

Address Resolution Protocol

What Does It Do?

The arp command shows or changes the ARP cache - a table that maps IP addresses to MAC addresses on your local network. Think of it like a contact list that connects names to physical addresses.

Every device on your network has a unique MAC address (physical hardware address). ARP keeps track of which IP address belongs to which MAC address so devices can talk to each other locally. Useful for network troubleshooting and security checks.

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When Should I Use It?

See Connected Devices

View all devices your computer recently communicated with on the local network.

Detect ARP Spoofing

Check for duplicate MAC addresses that might indicate a security attack.

Network Troubleshooting

Clear cached entries if you're having connection issues with local devices.

Find MAC Address

Look up the physical MAC address for a device on your network.

Common Commands

arp -a

Display the complete ARP cache table.

arp -a 192.168.1.1

Show ARP entry for a specific IP address.

arp -d 192.168.1.1

Delete the ARP entry for the specified IP address (requires admin).

arp -s 192.168.1.50 00-aa-bb-cc-dd-ee

Add a static ARP entry mapping IP to MAC address (requires admin).

arp -g

Same as -a, displays the ARP cache table.

Administrator Privileges Required

The arp -d and arp -s commands require Administrator privileges to modify the ARP cache.

To run commands as Administrator in the simulator:

1.
runas /user:administrator cmd

Request administrator privileges

2.
admin123

Enter the password when prompted

3.
arp -s 192.168.1.50 00-aa-bb-cc-dd-ee

Now you can add or delete ARP cache entries

Real Windows: Right-click Command Prompt and select "Run as administrator" before running these commands.

Try It Yourself

Practice arp commands in the interactive terminal below: