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8341
July 27th, 2016 17:00
Constant STP Topology Changes
Running a total of 8 different PowerConnect switches here. Models: 5424, 5324, 5524.
Topology:
The issue at hand is I'm monitoring for STP changes and there are constant topology changes occurring, maybe 15-20 times a day, but none of the root bridge ID's are changing. They stay the same (NSW001.)
When using show spanning-tree it is showing the number of topology changes increasing but the "last changed occurred" is not. In the below example, this switch has had easily 50 topology changes this week alone.
Example.
Number of topology changes 336969 last change occurred 163:49:06 ago
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
No Events found!
rpesta
5 Posts
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July 28th, 2016 13:00
That's the odd thing. Nothing related to the STP change is showing up on the logs in any of the switches, and the "last change occurred" time doesn't really ever change but the "number of topology changes" increments.
Checking the interfaces BDPU counters, they all show pretty high values, likely because these switches have been online for a while now. Haven't found a way to reset BDPU counters. "clear counters" doesn't work.
Here's what the data looks like. Anything with BDPU received I have listed.
NSW001
g2 330015 sent 472330 received (dumb switch that is going away)
g18 330047 sent 82 received (NSW006)
g23 330069 sent 156 received (NSW005)
NSW002
g22 18313245 sent 64171653 received (NSW003)
g23 73473996 sent 19 received (NSW004)
g24 74986290 sent 110360624 received (NSW001)
NSW003
g24 64171674 sent 18314374 received (NSW002)
NSW004
g24 4 sent 6107941 received (NSW002)
NSW005
g14 6165756 sent 1691695 received (wireless access point)
g17 6165664 sent 741 received (NSW007)
g19 6165532 sent 199960 received (wireless access point)
g23 6165777 sent 218429 received (wireless access point)
g24 2242 sent 6168603 received (NSW001)
NSW006
g2 980665 sent 704 received (wireless access point)
g23 419 sent 1548751 received (NSW001)
NSW007
g21 1465870 sent 358878 received (wireless access point)
g24 469 sent 1468431 received (NSW005)
Seems like maybe the culprit is the dumb switch we have setup connecting directly to NSW001? Doesn't exactly explain though why nothing is showing in logs and the "time since last change" doesn't reset to 0 after each topology change.
rpesta
5 Posts
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July 28th, 2016 13:00
It's a PowerConnect 5424
rpesta
5 Posts
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July 29th, 2016 18:00
I've disabled STP for port g2 but am receiving an error when trying to set the bpdu mode to filter.
am01nsw001(config)# spanning-tree bdpu filtering
% Wrong number of parameters or invalid range, size or characters entered
I've confirmed after disabling STP on the g2 port, the topology changes are still occurring.
rpesta
5 Posts
0
August 9th, 2016 16:00
Very odd. I've tried rebooting the switch and also confirmed I'm on the latest version of the firmware (2.0.0.46). ALL of our switches are on the latest firmware versions and no ports are set to portfast. Nothing is ever unplugged on a regular basis either.
Even more odd, it seems debugging simply doesn't work. Enabling debugging provides me no debug information when STP changes occur. Also as I mentioned earlier, the STP change time doesn't reset to 00:00, but the STP change number increases.