Document Number: OSUP1056
Product: Observer, All versions
Date: 5/26/2006
Title: "No VLAN" displayed when using Broadcom NetXtreme Gigabit NIC

Keywords: 802.1Q, Broadcom, VLAN, tag

SYMPTOM: "No Vlan" is displayed in VLAN Statistics and/or there is not 802.1Q tag information displayed in the decode. The NIC you are using to capture the traffic is a Broadcom NetXtreme Gigabit adapter.

REASONS: Observer is not seeing the 802.1Q tag on any other packets being captured. Usually this is caused by the switch not sending tagged packets to the Observer, so please check OSUP1052 for explanation/resolution before proceeding. http://www.netinst.com/support/osup1052.html

SOLUTION: If you are using a Broadcom NetXtreme Gigabit NIC to capture the traffic and you have checked the switch configuration. Then try using the fix below. For BCM5751M NetXtreme Gigabit chips found in in IBM T43, HP laptops, and Dell Latitude laptops; there is a registry key under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet that can be set to cause the driver and chip not to strip the 802.1Q headers. In order to set that key, you need to find the right instance of the driver in Registry Editor and set that key for it. You can do this by doing following:

1. Run the Registry Editor (regedt32).

2. Search for "TxCoalescingTicks" and ensure this is the only instance that you have.

3. Right-click on the instance number (eg. 0008) and add a new string value.

4. Enter "PreserveVlanInfoInRxPacket" and give it the value "1".

5. Reboot the computer.

This should set you up to be able to capture the VLAN tag information.