How many bits reserved in 802.1Q and ISL header for QoS?

[Jigar Dave]

Please help - How many bits are reserved in 802.1q and ISL header for QoS.

Thanks in Advance

-Jigar

[Peter Paluch]

Hi Jigar,

For 802.1Q, 3 bits are reserved, yielding 8 different CoS classes. For ISL, there appear to be 2 bits reserved for priority purposes, yielding 4 different CoS classes. See the following URL for more info:

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094665.shtml

Best regards,

Peter