Make Windows Prefer Wired LAN over Wi-Fi with a DHCP Default Router Metric

When a laptop is connected to both wired Ethernet and Wi-Fi, you usually want traffic to go over the wired LAN. If your Windows Server 2003/2008 DHCP server hands out the wireless addresses, you can make that happen automatically by giving the wireless gateway a higher route metric. Windows always prefers the route with the lower metric.

Set the Metric on the Wireless DHCP Scope

1. In the DHCP console, right-click Scope Options on your wireless scope and choose Configure Options.
2. Open the Advanced tab.
3. For Vendor class, choose Microsoft Windows 2000 Options.
4. Check 003 Microsoft Default Router Metric Base.
5. Enter a value that suits your network. I use 0x1f4 (500), which gives the wireless route an effective metric of 525, higher than every other network metric we use.

Optional: Set the Wired Scopes Too

You can repeat these steps on your wired scopes with a value of 0, which leaves them at the base metric of 10. This is only necessary if their current base value is higher than 10. Check it by running route print from a command prompt.

For more detail, see Microsoft’s TechNet article on DHCP options and search the page for “default router metric base”.