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TechKnowSurge Catalog Videos DEMO: Mac Address Table
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DEMO: Mac Address Table

A MAC address table on a network switch maps each device's MAC address to the physical port it occupies, which is distinct from ARP, which maps IP addresses to MAC addresses. This demonstration walks through reading a live switch MAC address table and verifying an entry using the ipconfig /all command.

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About this video

A switch MAC address table is a core component of how Layer 2 networks operate, storing a mapping between each device's MAC address and the specific physical port on the switch where that device is connected. This is distinct from ARP, the Address Resolution Protocol, which serves a different purpose: translating IP addresses into MAC addresses so that devices can communicate across a network. Understanding the difference between these two tables is foundational to network troubleshooting and design. In a live demonstration using a switch with a single external device connected, the MAC address table is examined directly on the switch. Among the entries associated with the switch itself, one entry stands out as belonging to an external laptop plugged into port 14. The MAC address displayed in the table corresponds to that physical connection, illustrating exactly how a switch learns and records device locations on its ports. To confirm the accuracy of the table entry, the ipconfig /all command is run on the connected laptop. The Ethernet adapter's MAC address shown in the command output matches precisely the entry recorded in the switch's MAC address table under port 14. This verification step demonstrates how switch MAC address tables can be read and validated in a real network environment, reinforcing how switches use this information to forward traffic efficiently to the correct port.

What you'll learn

What's covered

MAC Address Table on a Switch

Aligned to

CompTIA Network+
1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.
2.2 Given a scenario, configure switching technologies and features.
Cisco CCNA
1.13 Describe switching concepts
Cisco CCST Networking
4.5 Explain basic switching concepts
5.5 Run basic show commands on a Cisco network device
Cisco CCST Cybersecurity
2.2 Explain how network addresses impact network security

Key terms

Media Access Control
MAC
A sublayer of the Data Link layer that controls how devices on a network gain access to a medium and transmit data.
Address Resolution Protocol
ARP
A protocol used to map an IP address to a physical MAC address on a local network.
Switch
A network device that connects devices within a LAN and forwards traffic based on MAC addresses.
MAC Address Table
A table maintained by a switch (also called the CAM table) that maps source MAC addresses to the switch ports on which those devices were learned. When a frame arrives, the switch looks up the destination MAC in this table to forward it out only the correct port rather than flooding all ports.
IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.

Transcript

Just remember that a MAC address table is much different than an ARP, an address resolution protocol. ARP translates IP addresses to MAC addresses, versus a MAC address table, which associates a MAC address with the port it's on.

I have my demo laptop that's plugged into a switch. Looking at the MAC address table on the switch and scrolling through here, what we can see is this entry right here. I don't have a lot plugged into it, so we see a lot of MAC addresses that are associated with this switch, but this is the only other device that's plugged into this. So we see the MAC address of the demo laptop that's plugged in, and the port that it's plugged into. That is a MAC address table.

Verifying the address on the laptop

Just to verify that that is the MAC address of this machine, I'm going to open up a command prompt and do ipconfig /all. This is connected into the Ethernet port, so not the Wi-Fi. Here's the Ethernet port, and here's the MAC address of the port that's plugged into the switch. And it's plugged in on port 14, and we see that port 14. Yes, that is in fact the same MAC address.

So that's what a MAC address table looks like on a switch.

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