Which port to check via MAC address on the access switch

You can view all MAC addresses associated with a particular port using vendor-specific commands like show mac address-table interface on Cisco or show ethernet-switching table interface on Juniper switches.

Cisco Switches

To check MAC addresses on a specific port: Show all MAC addresses: CodeCopyshow mac address-table This displays all learned MAC addresses with their VLAN and port information. Check a specific MAC address: CodeCopyshow mac address-table address This shows the port where a particular device is connected. Check all MACs on a specific interface: CodeCopyshow mac address-table interface Example: CodeCopyshow mac address-table interface Gi0/1 This lists all MAC addresses currently learned on that port.

Optional VLA

N filtering: CodeCopyshow mac address-table vlan This shows MAC addresses for a specific VLAN. If the device is behind multiple switches, you may need to trace through uplinks using show cdp neighbors and check the MAC table on the access switch where the device is directly connected.

Juniper Switches

For Juniper E

X series switches: Show MAC addresses for a VLAN: CodeCopyshow ethernet-switching table orCodeCopyshow bridge mac-table Check MACs on a specific interface: CodeCopyshow ethernet-switching table interface This displays all MAC addresses learned on that port. Juniper also allows limiting MAC addresses per port or locking a port to a specific MAC to prevent flooding.

Using SNMP

If you prefer automated or remote monitoring: Use the dot1dTpFdbPort OID to find the port index for a MAC address. Map the port index to the actual interface using dot1dBasePortIfIndex.

Example SNM

P command: CodeCopysnmpwalk -v 1 -c public 1. 3. 6.

1. 2. 1.

17. 4. 3.

1. 2 | grep "INTEGER: " Then retrieve the MAC addresses associated with that port.

Summary

Cisco: show mac address-table interface Juniper: show ethernet-switching table interface SNMP: Use dot1dTpFdbPort and dot1dBasePortIfIndex to map MACs to ports. These methods allow you to identify all devices connected to a specific switch port, whether for troubleshooting, auditing, or network management purposes.