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link failure and stopping the inline power supply


CIPT document says that the inline power module of Cat6K(CatOS 5.5 or higher)/Cat4K (CatOS 6.1 or higher) automatically detects IP Phone by sending and receiving FLPs. Upon a receipt of FLP back from the IP Phone, the switch starts providing power. If the switch detects link integrity before the expiration of its 'wait-for-link' timer, it will maintain its power supply to the phone until it detects a link down event.

Now we have a question.

How about link down algorhtm/condition?

Does it, inline power port, follow the same convention as normal ethernet port? Does it declare a link failure after missing 3 keepalives? Then *HOW LONG* do we need to wait until the switch stops feeding the power to the port? This is an important question for us, service vendor. A user may connect his PC to the inline power port immediately after pulling off the IP Phone. If the switch does not stop its power supply within a short period of time, the user's PC is going to be affected. Please don't expect end users to follow a sort of "best practice". They will do whatever they want to do. And we need to have a precaution for such a case. Let us know the safety guideline.


Cisco Employee

Re: link failure and stopping the inline power supply

Here is a pretty good explaination of how the discover works for inline power.

Thank you,


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