10-26-2012 10:10 AM
I am currently experiencing a really percurliar issue with our network and I'm trying to get ideas on how to go about troubleshooting it. We currently use SX and FCX switches and really haven't had any significant issues for the two years I've been with this company. Just this week, our POE ShoreTel phones started losing connection and we had to advise user's to unplug phones and plug back in to restore the connection. Now it appears the ports are losing complete network connection and I am having to go in and bounce the ports, and in some cases physically switch ports to restore network connectivity. I am in the process of sifting through logs, however I'm not quite sure how to tackle this one or what it can be since the issue is spanning over multiple switches. I would assume that something like this would have to do with STP/RSTP, but again, I'm unsure how to approach it. Would anyone be willing to provide suggestions on how to properly troubleshoot this issue or where I should begin?
10-26-2012 09:20 PM
You might want to consider turning on BPDU guard on the physical interfaces that the phones plug into. Considering you shouldn't see BPDUs on those ports, BPDU guard would put those ports into an errdisable state if/when BPDU packets were detected on them. I can't think of any reason you'd be seeing BPDUs on those ports though.
For starting to troubleshoot, I'd probably try to ascertain a few things:
- Are the ports going "down" or are you losing IP connectivity to the phones? Check the state of the interface with "show interface....."
- When the problem is occurring, do you still see the MAC of the phone with a "show mac-address...." command?
- Also, it would be interesting to see if the IP of the phone is in the ARP table of the router when the problem is occurring.
You might also look at possible PoE related issues with "show inline power detail" (for starters).
This might not get you to a solution, but it will hopefully start to paint a clearer picture of what is, or isn't, going on.
10-29-2012 01:44 PM
Thank you for the feedback. I have BPDU guard enabled on "user" ports and I believe this issue started when two of the parts were errdisabled. I am sifting throw the logs and still troubleshooting to figure out the cause. It appears the port remains "up", however the end point loses connectivity. This is also happening with wireless APs and therefore affecting wireless. I am in the process of testing if the MAC is still being registered to that port or not and if the IPs are still in the ARP, however I'm not sure exactly what this will determine. In regards to the PoE, the consumption to allocation percentage is nearly 50% or below, so I would assume it is not a PoE issue. I'll keep investigating and troubleshooting and for now, the issue has seem to subsided. Thank you again for the feedback and providing some guidelines on determining the cause.
10-29-2012 05:08 PM
Good luck. In regards to what you will gain by knowing whether or not the MAC shows up in the switch table and/or at the router (with the ARP entry), that would definitely let you know whether to be focusing on the switch or the upstream router. If the MAC is the in the mac table on the switch, but dropping out of the router's ARP table, it might be good to focus on possible issues at the router. If nothing else, it would be interesting to know.
12-18-2012 06:48 PM
I stumbled across your post and was wondering if you solved your problem? I am having the exact same issue and pulling my hair out to resolve it.
Any assistance would be greatly appreciated!