The importance of Network Monitoring Systems (NMS)

One of our open tickets on MidWest-IX is a member reporting slow speeds on their exchange port. After having them send us some data and a few e-mails back and forth we began looking at their switch port on the fabric.  Right away we noticed errors on the port. After a counter reset the errors were still incrementing

 19 runts  0 giants  1210 CRC  0 no buffer
 1329 input error  0 short frame  0 overrun  0 underrun  0 ignored

This led us to look at our LibreNMS data for this port.  A quick look shows on October 31st the port started seeing input errors.

By drilling down we are able to see exactly when this started happening

We now have responded to the customer to see if anything changed that day. Maybe a new switch, new optic, or software upgrade.  By having this data available in an NMS we were able to cut down on troubleshooting by a huge margin.  We now know when the issue started and are closer to the root cause of this.  Without this data, we would be spending more time trying to diagnose and track down issues.

Cisco 2960X I/O usage

While double checking some stats on a network I came across this in Libre.   84% is usually something that would cause me to be alarmed, as Libre is trying to tell us.

After some research, I found the following.

While it is not documented, it was noted that this was by design and that it would not affect the switch as the switchport becomes more and more loaded.

The switch allocates dedicated memory to certain processes / resources by default and then additional resources when the configuration is added. This ensures proper functionality and is again by design.

The I/O Memory pool buffers information transmitted to and from the CPU, and does not affect the actual forwarding of packets on the switch.

Translation: The switch uses up these resources by default, even if they aren’t all being used.  Think of it as setting it aside for future use without dynamic allocation of them.

Thresholds for Microwave backhauls in Librenms

If you are running Librenms this video will help you learn how to adjust the thresholds for signal strength when it comes to microwave/licensed backhauls.  This video focuses on Mimosa because that was the quickest handy thing.  Cambium and other manufacturers will be slightly different due to chains being combined and other things.

Helpful Librenms commands for fixing broken installs

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