No VLAN” shown while using Broadcom NetXtreme Gigabit NIC

No VLAN” shown while using Broadcom NetXtreme Gigabit NIC

Symptoms: “No VLAN” is displayed in VLAN Statistics and/or no 802.1Q tag information is shown in your decode. The network adapter you use to capture traffic is also a Broadcom NetXtreme Gigabit NIC.

Causes: Observer is not seeing the 802.1Q tag on packets being captured. This is sometimes caused by your switch not sending tagged packets to Observer. See VLAN Statistics tool is not working for explanation/resolution before proceeding.

Solutions: 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. To set that key, you must find the correct instance of the driver in Windows registry and change it.

1 Open the Windows registry editor. Start → Run → Command and type regedit.

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

3 Right-click the instance number (e.g., 0008) and add a new string value.

4 Type PreserveVlanInfoInRxPacket and give it the value 1.

5 Restart the computer.

The Broadcom NetXtreme Gigabit NIC no longer strips VLAN tags, so the symptom in Observer is resolved