Communicating over TCP/IP May Fail Due to 802.3 Frame Type

 Last reviewed: September 9, 1996
Article ID: Q140913
The information in this article applies to:
  • Microsoft Windows NT Workstation versions 3.5 and 3.51
  • Microsoft Windows NT Server versions 3.5 and 3.51

SYMPTOMS

A Windows NT TCP/IP node is not be able to communicate to a non Microsoft based TCP/IP node.

CAUSE

The non Microsoft TCP/IP node is configured to use 802.3 SNAP encoding. Some devices can be configured to use 802.3 SNAP encoding. By default, the Microsoft TCP/IP stack transmits packets in DIX Ethernet format.

RESOLUTION

If the node device is using 802.3 SNAP encoding, modify the Windows NT registry and change the ArpUseEtherSNAP setting to 1 on the Windows NT system to match the 802.3 SNAP encoding.

Registry path:

This parameter is under the subtree HKEY_LOCAL_MACHINE under the following subkey: 

   \SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

     Value (Parameter) Name: ArpUseEtherSNAP
     Data Type:  REG_DWORD - Boolean
     Data Range: 0 or 1 (False or True)
     Default:    0 (False)
Description: Setting this parameter to 1 will force TCP/IP to transmit Ethernet packets using 802.3 SNAP encoding. By default, the stack transmits packets in DIX Ethernet format. Windows NT always receives both formats.

KBCategory: kbnetwork
KBSubcategory: nttcp
Additional reference words: 3.50 3.51 prodnt



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Last reviewed: September 9, 1996
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