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SG200 bringing down network

Hi All,

I have a SG500X with a SG200 and SG300 connected via LAG's.

The customer reported today their wireless network went down.

Sure enough after going on site I confirmed the LAP1042's connected to the SG300 were periodically connecting and disconnecting from the CT2504 connected to the SG500X.

Through various troubleshooting I found I also lost connectivity to the management interface of the SG200.

After much head scratching I found if I disconnected one of the SG500X LAG member ports to the SG300, connectivity was restored to the SG200 and all the LAP1042's.

Naturally that would suggest an issue with the SG500X or the SG300.

I confirmed the config on all switches was correct.

No errors in the logs of either the SG500X or SG300, however I did have errors in the SG200 log.

The following was repeated over and over;

2146810814   2010-Oct-14 14:01:07 Warning   %CDB-W-CDBOVERFLOW: Overflow in CDB       

2146810815   2010-Oct-14 14:01:07 Warning   %CDB-W-STCDBOVERFLOW: Overflow in startup CDB. offset = 131039, file end = 131040       

2146810816   2010-Oct-14 14:01:06 Warning   %CDB-W-CDBOVERFLOW: Overflow in CDB   

No amount of googling has come up with anything on CDB.

Anyone seen this error before or better still have any idea what it means?




CDB is Configuration Database Backup (as far as I know). One could only speculate why the CDB would have an overflow error. I know the switch has a "LKG" (last known good) feature which comes in the form of a mirror backup. I don't see how this would affect making a switch going up and down without causing a reboot.

You may want to look at your spanning tree root bridge, ensure your core switch is the lowest bridge priority. Also may want to ensure your LAG has the lowest priority for on the core switch per interface as well. I would almost like to speculate may be the configuration BPDU is purging the max age tables causing the over flow error due to a redundant election process. But that is a conspiracy theory at best.

Please rate helpful posts

-Tom Please mark answered for helpful posts
Rising star

Hi Gary,

I like toms answer, i am think along the same line .

You suggested that "I confirmed the config on all switches was correct."  what if by chance the LAG with LACP configuration is incorrect or there is a issue with firmware variations. A couple of things you could try if Toms suggestion doesn't fix the issue.

  1. it could be because of firmware, so make sure the SG200, SG300 and the SG500X are at the currently released version of firmware.
  2. If you upgrade firmware on the switches fixes the problem great but if not, It would be interesting as a next step  to simplify your design by getting rid of the LAG on all machines  and just starting with a single link between switches.  All Vlan interfaces should be trunked by default so no need to change the VLAN interfaces from trunk mode.

lets see if the switch network is stable and the error messages disappear.

regards Dave


I confired the root bridge and updated the firmware on all the devices to the far all is good.

Many thanks to you both for your help.