Symptoms

Do you want to determine the passthrough MAC address on your laptop? Note: There are many different reasons why you must know this information. (For example: Adding it to the approved list.) However, this article assumes that you have a valid reason. Pass-Through Media Access Control (MAC) address is also known as the Virtual MAC address, or the Auxiliary MAC address. This is a feature that Dell named MAC Address Override or MAC Address Pass-Through. It uses a MAC address that is unique to the laptop. It is entered in the Basic Input Output System (BIOS). It overrides the dock or dongle MAC address every time that it connects to the network. Laptops that are joined to a managed network often rely on Static IP Addresses. This ensures that these assets comply with the availability and discoverability requirements of the managing IT group. Unique hardware MAC Addresses are used to identify and manage individual assets on a network. However, when a docked laptop is configured with a Static Internet Protocol (IP) Address, the dock can block any MAC Address pass-through communication. It prevents your IT from managing the laptop on the network when the laptop is on a docking station. (This is due to the dock running the default Dynamic Host Configuration Protocol (DHCP) IP Address configuration.) Assigning and configuring a Static IP address on the dock ensures that the MAC Address pass-through functions properly. This ensures that the docked Static IP laptops are manageable on the network.

Cause

This is due to a limitation of the MAC Address pass-through for docked laptops. MAC Address Pass-Through does not work even when it is enabled in the BIOS.

Resolution

Steps to determine the passthrough MAC address With the USB-C Dock or network adapter, attached: From a command-line prompt run either of the following commands: GETMAC Or IPCONFIG Without the USB-C Dock or network adapter, attached: Use the BIOS: Start the laptop and tap rapidly on the F2 or F12 key at the Dell Splash screen to enter the BIOS. You can find it under System Information. Steps to enable MAC Pass-Through in the BIOS: Start the laptop and tap rapidly on the F2 or F12 key at the Dell Splash screen to enter the BIOS. Go to System Configuration and locate: MAC address Pass-Through: System Unique MAC Address Select Enable. Save your changes and restart the laptop. Workaround #1 If the MAC Pass-Through is already enabled in the BIOS, but this is not reflected inside the operating system? You must update the BIOS and the Dock Network driver (Realtek Gigabit Ethernet (GBE).) Install the latest update revisions available from the Dell Support site for your laptop. Workaround #2 In Windows settings: Go to Network & Internet settings. Select Change Adapter settings. Locate the Network Interface Controller (NIC) for your Dock (typically Realtek GBE Ethernet) and right-click it and select Properties from the menu that appears. Go to Configure and click the Advanced tab and then Network address. Type in the MAC address of your host laptop.

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