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Cisco WLC 5508 SNMP Monitor

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We have a Cisco WLC 5508 that we want to monitor using PRTG. I downloaded the MIB from Cisco and converted it using the Import Tool. I would like to monitor all of the traps but when I let PRTG create all the sensors it found based on that OID it created 932 sensors all of which where named something incoherent.

So I decided to dig through the MIB and only use the AP Name OID and create sensors based on that, which works, it scans the WLC and finds all of the attached APs and pulls their name. Great right?

Not quite, we have all of our APs set to fail over between our Austin office and the New York office controllers, whenever an AP fails over or gets disconnected for some reason the sensor freaks out and changes it state to "No Such Instance (SNMP error #223)". Now we do want it to alert when a device is no longer controlled by the controller but we need a little more information in the notification. As it sits right now when we get a DOWN it only tells us on which controller, but not which AP. Below are screenshots of an UP and DOWN notification. My question is this, how to I get it to input the name of the AP in the notification instead of No Such Instance in the notification?

cisco-ap cisco-wlc prtg

Created on May 9, 2016 7:53:49 PM



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Accepted Answer

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Hello Glynn,
thank you for your post.

Regarding the setup, it sounds like a good place to employ the SNMP Custom Table Sensor(click for instructions). It's also advisable because it supports auto-discovery for new aps or when failover takes place.

But the issue with (No Such Instance (SNMP error #223) ist most likely something that won't be possible to avoid within the built-in sensors. This happens because of the following:

There's currently a table, which looks roughly like this:

IndexNameStatus
1AP11
2AP21
3AP31

Each line of the table will be uniquely identified by a index, for instance .1, .2 and .3. Now you need to imagine that when an AP "fails-over" it vanishes from the table on controller 1 and shows up in the table on controller 2. When this happens PRTG will try to query the OID with index (e.g.) 2 on the old controller but that entry will be "gone", thus error No Such Instance .

Available Options

1. If you employ the previously mentioned Table Sensor you can come-up with a Name Template which assigns meaningful names to the sensor such as "AP1 on Controller NY", which will make the messages more meaningful but will still mean that you will require 1 sensor per AP on each controller and you will always have "down" sensors for the controller that is missing the other AP's, unless you pause these sensors.

2. Alternatively, you may use a powershell-script/custom exe/sensor to walk both controllers and come up with a virtual device which will the AP's "summarized" or even a sensor to count the number of AP's per controller and status, similar to the BGP sensor. This would not be a simple script to implement I'm afraid.

Best Regards,

Created on May 10, 2016 9:01:10 AM by Luciano Lingnau [Paessler]




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