You can check a core switch's MAC address using the show version command for the switch itself, or show mac address-table to view MAC addresses learned on its ports.

Checking the Switch's Own MAC Address

To find the MAC address of the core switch itself:

1. Log in to the switch via console, SSH, or Telnet.
2. Enter privileged EXEC mode by typing enable.
3. Run the command:

   show version In the output, look for a line like:

   Base ethernet MAC address: 0007.ECE1.5D18 This is the switch's primary MAC address, often used for STP and VLAN 1 interfaces .

Checking MAC Addresses on Switch Ports

Each switch port may have its own MAC address, especially on Layer 3 switches or routed ports. To see MAC addresses learned on each port:

1. Enter privileged EXEC mode.
2. Run:

   show mac address-table This displays a table with VLANs, MAC addresses, type (dynamic or static), and the port where each MAC is learned .

3. To find a specific device's MAC address and its port:

   show mac address-table address <mac-address> Replace <mac-address> with the device's MAC. The output shows the VLAN and port where the device is connected .

Tracing MAC Addresses from Core to Access Switches

If you are on a core switch and want to find the MAC address of a device connected to an access switch:

1. Use show mac address-table on the core switch to see which MAC addresses are learned on uplink ports to access switches.
2. Identify the port connecting to the access switch.
3. Log in to the access switch and run the same show mac address-table command to locate the exact port of the end device .

Additional Tips

• For managed switches, you can also use LLDP or CDP to discover connected devices and their MAC addresses.
• Ensure the switch's management IP is reachable if using ARP or network-based queries.
• Remember that unmanaged switches may not provide per-port MAC addresses or support these commands . By following these steps, you can identify both the core switch's own MAC address and the MAC addresses of devices connected through it, which is essential for network monitoring, troubleshooting, and configuration.