Sunday, September 10, 2017

High CPU on Nexus 3K - Solved

In this blogtorial, I will demonstrate how I used 'ethanalyzer' on a Cisco Nexus 3K to solve an intermittent issue -- random adjacency drops of various routing protocols. Before we get into the details. let me first share with you on how I got involved in this troubleshooting to begin with. My good friend and colleague "BGP" bill aka self proclaimed "Multicast Guru" 😊 turns around says "Hey Weezy, you are a CCIE right? I have an open case with Cisco for a month why don't you just solve this issue?". Hmmmm ... above all else, one thing I've learned from the journey of becoming a CCIE is that I know very little. There is so much more to learn than you can imagine. In any case, I thought it was a noble challenge and as a bonus it peaked my curiosity. So Bill and I started chatting about the issue and as we were going through the motions, he gave me a great piece of information that would eventually steer me down the path to solving the issue, "Pete reported that he saw HIGH CPU usage compared to other similar routers".

So my 2 questions were:

Tuesday, January 10, 2017


Well it is official. I've signed up for a git hub account. I can now start publishing some open source tools on my free time to help my fellow engineers and tech enthusiasts.

Here is the link to my git repo that you can clone for yourself and contribute or use it.

Sunday, January 1, 2017

Interaction between TLP (Tail Loss Probe) and SolarFlare EF_DYNAMIC_ACK_THRESH

In this blogtorial I will briefly discuss a performance issue that had me stumped for a bit. But after some googling around I stumbled up on the answer. I then started to take apart the RFC to gain a better understanding at the mischievous protocols at play. Oil powers the world and water sustains life, however they do not mix well together and the same concept applies here. Tail loss probe on its own is a great feature reducing the time it takes to detect packet loss and makes the TCP connection much more efficient. SolarFlare EF_DYNAMIC_ACK_THRESH is also a great feature which helps TCP performance. But enable these features at the same time and your TCP performance will suffer greatly.