Changing the properties on a physical adapter that is bound to a virtual switch is not supported.

  • Article

This article describes a known issue where changing the properties on a physical adapter that is bound to a virtual switch is not supported.

This article applies to the following operating systems:

  • Windows® Server 2008 R2

  • Windows® 7

Symptoms

When a switch gets created the existing settings associated with the physical adapter gets transferred over to the virtual miniport that gets created as part of the switch creation process. e.g.: If TCP/IPV4 protocol was bounded to the adapter before switch creation, enumerating the network properties of the physical adapter would show it as unbounded after a switch gets bounded to it . The operating system stops unexpectedly and an error message appears on a blue screen.

Cause

If tcp/ipv4 or tcp/ipv6 protocol is already bound to the miniport associated with the physical adapter, perform the following steps.1.Enable forwarding on the physical adapter 2.Bind the tcp/ip protocol back to the physical adapter

Enabling TCP/IP on the physical NIC when the switch protocol is already bound is not a valid configuration.You also need to enable ip forwarding via netsh.This looks like an infinite loopback/ip forwarding bug. The swtich just passes the NBL (net buffer list) along to the physical NIC but ndis loops it back to TCP is forwards it back to the switch (and so on and so on and so on). I've sent an email to the ndis and tcp teams to see if there is anything the switch can do to prevent this loop or if this is a known issue with intermediate drivers.

Workaround

What should the user do to avoid this?======================================Changing the properties on a physical adapter that is bounded to a switch is not a supported.How can the user fix the problem if they encounter it?======================================================Unhook the cable, reboot the machine and unbind the tcp/ip protocol associated with the adapter