[cisco-voip] Cisco 8851 and MSTP

[Ryan Ratliff (rratliff)]

CSCut26167, fixed in 10.3.1.

https://tools.cisco.com/bugsearch/bug/CSCut26167


Symptom:

A switching loop occurs when an 88xx phone has its network and PC port connected to the switch when the phone does not forward the BPDU

Conditions:
This has been found to occur on switches using MST. With other types of spanning tree, this issue has not been observed.

Workaround:
Do not use MST, or use another phone model.


-Ryan

On Jul 8, 2015, at 2:47 PM, Michael David <mdavid at sps186.org<mailto:mdavid at sps186.org>> wrote:

Just a heads up to anyone running 8800-series phones and using MSTP.

We're in deployment of a new 10.5 CUCM system with 8851 and 7841 phones.  A few times now we've been hit with network loops as janitors empty rooms to clean/wax and then replace stuff, plugging in everything they see loose. The loops have only been happening with 8851 phones.  With the 7841 phones, bpduguard shuts down the phone almost as soon as connected. With the 8851s, the loop runs unchecked.. and affects the entire site, almost like the phone is filtering BPDUs. However, I took a phone and switch into the lab, and after a little testing have found that the problem only occurs when using MSTP.

Switch: WS-C2960XR-48FPD-I
Switch firmware: 10.0(2)EX5
Phone firmware: 10.2(2)
Test case log: http://pastebin.com/gm5emaZa

I can't currently test this with the 10.3 firmware, but I saw no mention of spanning tree in the 10.3 release notes. In the short term, I'll probably have to switch all of our switches to rapid-pvst. Convergence with non-cisco equipment will be slower, but that's the lesser evil here. Hope I've saved someone else some grief. :-)

Michael

--
Michael A. David, CCNA
Springfield Public Schools
Technology Service Center
217.585.5802 ext. 85114
217.585.5809 (FAX)

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