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Strange behavior regarding POE power on Catalyst 4500 L3 Switch Software (cat4500-IPBASEK9-M), Version 12.2(37)SG


Hi everyone,


I've observed very strange behavior regarding POE power configuration on Catalyst 4500 L3 Switch Software (cat4500-IPBASEK9-M), Version 12.2(37)SG. BTW this is WS-C4506 with sup WS-X4013+


The line cards are all WS-X4548-GB-RJ45V and this occurs when one needs to use an external injector since these cards do not provide 30W needed for things like new APs etc The injector used is AIR-PWRINJ6V01


The injectors are designed as to detect whether the port provides POE and if it does the injector shuts down and becomes a pass-through which is exactly what one does not  want. The best practice is to turn off POE on the port. Then the injector detects that no power is present on the port and it provides the 30W which is what the whole setup is supposed to look like. That's where things get interesting.


If one simply configures the port "power inline never" the port does NOT provide POE anymore but there's some voltage still present on the pairs which is enough for the injector to detect it as POE and go into a pass-thought mode. 


To "fix" this one must issue first (example on Gi3/30) "default interface gigabitEthernet 3/30" and then copy the old config back -- totally unchanged; the same exact config as it was before the default command was issued only NOW the POE on the port is truly shut down. The injector no longer false positively detect the presence of POE on the port and all works as expected.


What the heck? Anyone seen this before?
Thank you


2 Replies 2

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend
Now that truely is a bug.

@Leo Laohoo Is there an IOS accessible command which resets the individual VRs on each port; maybe reset the controller ONLY on that port (not knock out the whole line card) or any other hardware port-specific reset one can do in order to avoid the "default" business; it's just a hassle and it might provide more insight into the issue at hand? I am imaginging something like "reset power module on Gi3/30)?



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