How do you find the MAC address of a device on a local network? Learn how the “arp -a” command displays IP-to-MAC address mappings—essential for Cisco Certified Support Technician (CCST) Networking 100-150 exam success.
Table of Contents
Question
A network technician needs to find the MAC address of a device on a local network. Which command should be used?
A. nslookup
B. ping -t
C. route print
D. ipconfig /release
E. arp -a
Answer
E. arp -a
Explanation
ARP (Address Resolution Protocol) shows a list of IP-to-MAC address mappings.
To find the MAC address of a device on a local network, use the arp -a command.
The arp -a command displays the Address Resolution Protocol (ARP) table, which maps IP addresses to their corresponding MAC addresses for devices on the same local network segment.
To ensure the device appears in the ARP table, first ping the device’s IP address. This forces your computer to communicate with the device, updating the ARP cache.
After pinging, run arp -a in the command prompt (Windows) or terminal (Linux/macOS) to view a list of IP addresses and their associated MAC (physical) addresses.
This method is effective only for devices on the same subnet, as ARP does not traverse routers.
Example Steps:
- Open a command prompt or terminal.
- Ping the device’s IP address (e.g., ping 192.168.1.10).
- Enter arp -a to display the list of IP-to-MAC address mappings.
arp -a shows the ARP table, listing all known IP and MAC address pairs on the local network.
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