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Thursday, May 26, 2011

Sniffing COS and VLAN ID

Had a hard time to find COS bits and Vlan ID in all my captures to prove QOS settings for a Nexus 2k switch.  At the end had to use a hub (a old 10 BaseT Ethernet hub, the reason had to use a mini switch before connect to a Nexus 2k port), a mini switch and a old RealTek NIC to get the capture showing the 802.1q tag.  Later found these url http://wiki.wireshark.org/CaptureSetup/VLAN and http://www.intel.com/support/network/sb/CS-005897.htm that explained almost everything.
Below is a Frame showing the COS and VLAN ID.

And here is the Ethernet Frame with 802.1q fields

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