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jasyoung Wed, 05/21/2003 - 17:39
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802.1q is the standard defining how to send frames between switches or other devices in multiple VLANs, by tagging the frame containing VLAN and other information about the frame. This is how you build "trunks" between switches. Cisco's ISL is a proprietary protocol that does the same thing.


802.1p is a standard for tagging frames with priority information for QoS, so that switches with multiple output queues can prioritize high-priority frames. It also has a role in multicast registration and filtering, but I don't believe this part is widely implemented.

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