Troubleshooting a port issue

Dwillcocks_2 · ‎12-09-2010

Hi,

We have a core stack of Cisco 3750 switches. We use Avaya 4621 IP phones with PoE from the switches.

I have one port that gives this error approx three or four times a week, at no set time of day

052545: Dec 9 09:55:08.396 UTC: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet9/0/45, changed state to down
052546: Dec 9 09:55:10.417 UTC: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet9/0/45, changed state to up

The PoE does not seem to be affected as far as I can tell but the phone is disconnected and when it comes back it cannot obtain a DHCP address. Only when I manually reboot the phone does it work again.

I have changed the physical phone but it has made no difference, I'm not able to change the network connection point although cable testing reports everything is fine.

What would be the next option to further troubleshoot this?

Dave

Peter Paluch · ‎12-09-2010

Dave,

One thing coming to my mind is to try using a different port instead of Fa9/0/45 if possible. That way we could eliminate a physical port problem. There may be some issues with that port in particular. If the problem keeps appearing then either the cabling is faulty (despite the measurements), or the phone just does not get along with the Cisco switch - sometimes that happens.

Also, are there any connectivity issues if the phone is powered using an external power supply?

Best regards,

Peter

Dwillcocks_2 · ‎12-09-2010

Thanks,

I have just been to look at the issue again and it has become even odder. Yesterday a reboot of the phone resolved the issue, today it did not and the phone would simply not obrtain an IP address.

I connected it to a different port on the switch with no change, I changed all the cabling, still no change. Finally changed the physical phone and all worked again (I had tried resetting and clearing the original phone first). So this is the second time that this station has developed a faulty phone?

When the DHCP issue was occuring I connected the laptop directly to the port and it too did not obtain an IP address. The laptop is set to autoconfigure and has a Gb NIC but there was no change in the port speed duplex, it remained at 100/full as if there was no communication between laptop and port.

Anyway, thanks for your suggestions, I will keep an eye on it and if the issue persists I may be updating this post fairly soon!

Dave

glen.grant · ‎12-09-2010

Check the speed/duplex on the switch and make sure it matches whats set on the phone. If the phone is set as auto then the switch has to be auto also . Also check to see if portfast is on for the port , may be why you have to reboot after it goes down if its not.