HP 2610-24-PWR and PoE on Cisco 7940 IP Phone

[Simon Christensen]

I have a problem with several 2610-24-PWR switches and PoE on Cisco 7940 IP Phones.

For making the Cisco 7940 Phone work on the 2610-24-PWR switch, I need to use a cross-over cable and enable the "power pre-std-detect" feature on the switch.

For the most of the phones it just works. They power on and gets network connectivity.

BUT some of the phones (and it is random) do NOT power on. There is Link on the switchport but NO power.
If I then unplug the the phone and plug it in again, then sometimes the phone gets power.
If the the switch is reloaded, then there are some OTHER Phones having this power problem.
It is compleatly random which Phones there gets power and which that don't.

I have tried upgrading/downgrading firmware (11.25 and 11.30) on switch, and it is still the same issue.
I have tried with 4 different 2610-24-PWR and it is still the same.

I have tried to reproduce the problem with only 1 phone on the switch, and again it is random if is gets power or don't. Even after a reload.

I have also tried with 3 different 2610-24/12-PWR and on these switches there are NO problems at all... They just work.

I'm out of ideas...

[cenk sasmaztin]

please disable cdp on switch

config)#no cdp

and say me result

[Simon Christensen]

Ok. Did a "no cdp run" and that disabled CDP, but nothing has changed regarding the IP Phones.

It is still random if the Phone gets Power or not.

[cenk sasmaztin]

please send me sh tech print your switch

[Simon Christensen]

Did a "show tech" see attached document.

What I didn't notice before is the line in the log "port 1 PD Invalid Signature indication"

I guess thats the problem. But I don't know how to solve it.
Perhaps all the switches are defect... Or it works as designed and the 2610-24/12-pwr just is more tolerant.

[cenk sasmaztin]

Port PD Invalid
Signature indication.warning

The switch has detected a non-802.3af-compliant device on the port.
This message appears for all non-802.3af devices connected to the
port, such as other switches and PC-NICs.

that is exactly your ip phone does not support 802.3af for hp switch


ip phone do full upgrade

[Simon Christensen]

IP phone re-loaded with new firmware.

Nothing new... Still the same Power issue.
Random if the phone gets power or not.

[cenk sasmaztin]

can you single test with me

connect with straight-through patch cable your ip phone on switch
and set 100-full ip phone ethernet port

and write this command on switch port

sw1(config)# interface 1
sw1(eth-1)# speed-duplex 100-full
sw1(eth-1)# mdix-mode mdix


please test and say me result

[Simon Christensen]

If I use a Straight-through cable then I get no Power at all
I then use a Cross-over cable I sometime gets Power.
I have tried to lock the phone to 100-Full and the switchport to 100-Full and MDI.

It is still the same result.
Some times the Phone gets Power and sometimes it don't.

[cenk sasmaztin]

How much Power-over-Ethernet (PoE) wattage is available?

The 2610-24-PWR and 2610-48-PWR both have an internal power supply that can provide up to 406 watts of power to PoE devices.

For the 2610-24-PWR, thatâ s enough to supply 15.4 watts per port for all 24 10/100 ports, which is the maximum allowed by the 802.3af specification for Power Sourcing Equipment.

For the 2610-48-PWR, 406 watts is enough for 24 ports at the maximum allowable wattage, or all 48 ports at an average of 8.4 Watts (most IP phones do not require more than this)

For the 2610-24/12PWR, there is 126 Watts, enough for 8 PoE ports at the full 15.4 Watts per port, or 12 ports at an average of 10.5 watts per port.

[Simon Christensen]

Well it is a 2610-24-PWR and as you say it can provide 406W totally.

I'm only testing with 1 (one) phone, and it uses 1897mW witch is about 2W
The phone is not even close to the 15.4W which is maximum for the port.

I think the problem is that the switch doesn't detect the phone correctly half of the times.

If the phone is detected as a Power Device (PD) then the switch provide power just fine.

It is just a mystery why the 2610-24-PWR fails and then smaller 2610-24/12-PWR just works.

I'm going to RMA these switches, and hopefully the new I get in return just works.

Thanks a lot for you help.

/Simon Christensen

[Drew Redman]

Those phones are pre-802.3af standard devices, so the crossover cable is absoluteley required since the phones are dependant on the DC voltage polarity. Pre-std-detect will likely also be required, as you have discussed.

Beyond these two things, there's nothing else you can do to increase compatibility. There may be nothing wrong with the switch(es) at all. Do you have a 802.3af compliant device to verify this?

[Simon Christensen]

I have tried with several 802.3af cisco 7941G phones, and they all work.

There is only problems with pre-802.3af phones

Cross-over cable and "pre-std-detect" used pre-802.3af phones.


When I connect a pre-802.3af phone it is random if it gets power
When I connect a 802.3af phone, power is provided all every time.

[Goh Kian Seng]

hi.. i'm getting the exact same problem now.. do u manage to solve the problem now ? mind share how you solve it?