Cisco IP Phone 6900 series port flapping

[Farhan Khan]

Hi All,

I have a Cisco WS-C3550-24-PWR switch to which I have connected a 7942, 7962, 6911, 6921 and 6941 phones. Both the 79XX phone register with Call Manager BE (version 8.5). However, none of the 69XX phone register. Configuration on th ports is same for all the phones. On the switch, ports connected to 69XX keep flapping ever few seconds and the phone appears to be just power cycling. Tried to connect the all the phones to 3524 XL switch and again 79XX registered but 69XX didn't even turn on (ports stayed down down). I was able to register all the phone when connected to a Cisco 3750 switch.

3550 IOS version: c3550-ipservicesk9-mz[1].122-40.SE.bin

Call Manager BE version: 8.5.1

Are their known issues between Cisco 3500 series switches and Cisco 6900 phones?

Does 3524 XL need any extra confirguration for 6900 phones?

Any help would be appreciated!

[pascal · Accepted solution]

The 6900 series phones are 802.3af only.  They do not support Cisco pre-standard PoE.

The 3524-PWR-XL is Cisco pre-standard only.  The 6900 series will never work on them.

The 3550-24PWR is not 802.3af compliant, however, it will power 802.3af compliant devices.

There is a common problem using newer PoE devices with 3550 switches whereby the devices take so long to establish link (or drops link during initiation) that the switch believes there is a problem and kills power to the device.  The work-around is to add the interface configuration command "power inline delay shutdown 20 initial 300".

Please report back on your results.  I have yet to try the 6900 series with my 3550s but I am considering doing so.

[rfovrtega]

Hi Pascal,

We have the same issue as you have. Did you make it work, the 69XX to power it up successfully to 3550 switches?

My IP phone is C6901, the phone blinks its led but no IVR prompt we can get, even reorder tone that verifys if it successfully get its power to 3550 switch.

[Farhan Khan]

Thanks Pascal,

We installed the phones on customer switches, I think Cisco 3750 and they all worked fine. However, this issue kept bugging me until you answered it above.

Thanks,

Farhan