3850 Switch port will not respond when moving IP phones

[tsutherland]

I have a stack of 9 3850-48P-S switches that are running version 03.06.05E of cat3k_caa-universalk9 software image.

They have IP Phones plugged in - various models, 7940, 7960, 7970, 8811, 8861 etc.

This is the typical switchport configuration:-

interface GigabitEthernet8/0/25
switchport access vlan 2
switchport mode access
switchport voice vlan 700
no mdix auto
spanning-tree portfast
spanning-tree bpduguard enable

VLAN 2 is for data and VLAN 700 is for voice - ip routing is enabled.

Observations are that when a phone is unplugged from one port and an alternate phone is plugged into the same port the switch will often refuse to power up the phone.  A laptop or desktop plugged into the problem port will come up.

The only way we can resolve this at present is to shutdown and then no shutdown the port.

Has anyone any ideas on how to resolve this?

[Manish Gogna]

You can refer the following doc for troubleshooting PoE issues

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/troubleshooting/g_power_over_ethernet.html#wp1016670

Manish

[Mohammed al Baqari]

Enable term moni on the switch and share the syslog messages which you connect the phone.

Also, if you enter the command 'show power inline' what is the output for that port.

[m.batts]

It could be the port is going errdisable ,  have you checked that?

[Adam Pawlowski]

Following this thread - I have heard about this from some of our guys here but haven't been able to observe it myself or look at it further.

One of our test tools (Fluke LinkRunner AT) will test PoE at different load and draw levels, and plugging this in seems to "kick start" the port into providing power. 03.07.04E.

[Brandon Buffin]

Seems related to this bug - https://bst.cloudapps.cisco.com/bugsearch/bug/CSCup05919. Neither of the releases mentioned in this thread are listed as affected versions. I would recommend opening a TAC case to see if they can tie the behavior to this bug.

Brandon