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Community Member

Port based Priority, tagged v. untagged

Forgive me if this is the wrong place to post this, but that's what being new is all about!

I am trying to find information for a contact who has asked the following quesiton:

What is the difference between Port-Based (Default Priority for Untagged Packets) and Port-Based (Overwrite Priority for Tagged Packets) in terms of classification?

Can anyone direct me to a document or give some insight on the differnce?

Thanks in advance!

Bill

2 REPLIES
Bronze

Re: Port based Priority, tagged v. untagged

See if this clarifies the issue: From

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat2940/12119ea1/2940scg/swqos.htm#1031793

Port Priority

"Frames received from users in the administratively-defined VLANs are classified or tagged for transmission to other devices. Based on rules that you define, a unique identifier (the tag) is inserted in each frame header before it is forwarded. The tag is examined and understood by each device before any broadcasts or transmissions to other switches, routers, or end stations. When the frame reaches the last switch or router, the tag is removed before the frame is sent to the

target end station. VLANs that are assigned on trunk or access ports without identification or a tag are called native or untagged frames.

For IEEE 802.1Q frames with tag information, the priority value from the header frame is used. For native frames, the default priority of the input port is used."

Community Member

Re: Port based Priority, tagged v. untagged

Hey, thanks for the reply.

The link is good and describes exactly what I thought it was. I did not express it as clearly to my contact as this, but at least I was on the "right" page! I'm going to forward to link and see if there are any other questions.

Thanks again,

Bill

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