Network Bridging Registry Settings (Compact 2013)


The registry stores information necessary to configure the system for applications and hardware devices. The registry also contains information that the operating system continually references during operation.

Windows Embedded Compact uses the registry to control the miniport drivers that are bound to a network bridge. The registry settings for the network bridge are stored under the HKEY_LOCAL_MACHINE\Comm\Mbridge registry key, which stands for Media Access Control (MAC) layer bridge. The name of the protocol driver for the bridge is MBRIDGE. When optioning, the bridge exports the MBRIDGE1 adapter by reading the adapter name and additional configuration information from the registry. For more information on configuring the registry for a network bridge, see Network Bridging Sample Registry Configuration.


The default registry values vary depending on which Catalog items are included in your OS design.

The following table shows the registry settings for HKEY_LOCAL_MACHINE\Comm\Mbridge.

Value : type



Specifies the allowable adapter for MBridge to bind to. Default value not set in the registry. This entry is required and must be filled out by the OEM.

The Bind value is the key enabler that informs the MBRIDGE protocol driver on which adapter it may bind to.

For each network adapter that binds to the MBRIDGE protocol driver, it is recommended that you set the ProtocolsToBindTO registry value under the [HKEY_LOCAL_MACHINE\Comm\<adapter name>\Parms] to "MBRIDGE" to make sure that the adapter is not bound to any other protocol, such as TCPSTK.

The TCP/IP protocol driver currently binds to any adapter that matches its medium type. By using the combination of the ProtocolsToBindTo registry key at the adapter level, and the Bind key at the MBRIDGE level, you can prevent the adapter from binding to multiple protocol drivers.


Spanning tree algorithm (STA) is enabled by default if this value is not specified. Enables or disables STA.

Fanout : REG_DWORD

Default setting is 32. Specifies the factor that is used to multiply the number of packets allocated to a copy path to determine the number of packets that are allocated to a non-copy path. For example, if the value is set to 32 and there are 100 packets in a copy path, 3200 packets are allocated to the non-copy path.

Linkage\Route : MULTI_SZ

Default setting is MBRIDGE1. Specifies the adapter name exported by MBridge.

MaxBufferMemory : REG_DWORD

Default setting is 200 Kbytes. Specifies the maximum amount of memory resources used for buffering.

MaxTableMemory : REG_DWORD

Default setting is 100 Kbytes. Specifies the maximum amount of memory resources used for forwarding table.

SafetyMargin : REG_DWORD

Default setting is 10%. Specifies the percentage of memory that is used as a safety margin.

AdapterNameForMBridgeMACAddress : REG_SZ

Contains the adapter name that MBridge will use as its default gateway Media Access Control (MAC) address.

When this value is set, the specified adapter does not need to support promiscuous mode and the private bit of the MAC address (0x020000000000) will not be set.

The following code shows how to set the value for an adapter named "PCI\NE20001"


Restricted Interface

Network bridging supports the configuration of restricted interfaces through the registry. To configure a restricted interface, set the RestrictedInterface value under HKEY_LOCAL_MACHINE\Comm\<adapter name>\Parms] to 1. Setting this value to 1 causes multicast/broadcast packets that are sent to one of the interfaces in the restricted group not be forwarded to other interfaces in that group. You may choose to enable this option if you are bridging multiple interfaces that have differing bandwidth or Quality of Service (QOS) requirements.


Setting the RestrictedInterface value may interfere with communication between hosts on two restricted interfaces. This setting is primarily intended for scenarios in which the restricted interfaces are dedicated primarily to a fixed purpose such as media streaming.

The following registry key example shows how to set the RestrictedInterface registry value for two different network adapters.


See Also


Network Bridging Sample Registry Configuration

Other Resources

Network Bridging Reference