routerjockey

Well-Known Intervals

Listed below are many events which occur on network devices at well-known intervals. The list is provided to serve as an aid while troubleshooting recurring network disruptions. …

Cisco ASA Packet Captures for Fun and Profit

As many of you know my background isn’t in enterprise, but I currently fill that role in my $job. In order to succeed I’ve had to develop many new skills including …

Nexus 1000v – Out of Ports on a Virtual Switch?

Yesterday, work presented an interesting issue I wanted to share with everyone. While configuring a new virtual machine one of our systems engineers was presented with an issue he …

IOS Embedded Packet Capture

Tired of setting up SPAN sessions? Need to do some packet analysis? Since IOS 12.4(20)T Cisco has made Embedded Packet Capture (EPC) available. EPC is a powerful troubleshooting …

Measuring Cable Lengths on a Catalyst Switch

A while back, I was playing on a 3750 switch in a customers lab and came across something I’ve never seen before. It seems that some Cisco switches have a built in …

Netcat – secret weapon

Netcat or nc, is a forgotten tool in too many arsenals these days. It lays dormant waiting at the command line to make connections across the globe for you. Knowing how to use it, …

Mail Server Relay Testing

As you may know, I am not big in the server world, even less into mail servers. They make me sick. But, today I found a nifty little tool you can use to test your mail server …

Testing TCP Connectivity on Cisco Devices

Ever thought you might be having some Layer 4 connectivity issues? Pings as you should know are ICMP transmissions and ICMP is a Layer 3 protocol (commonly used to send error …

How does latency effect throughput?

Tony Mattke
Routing
2 min read

One of the questions I get asked several times a week by my clients is as such. While most people never associate latency with the amount of data they can send across a single TCP …

Troubleshooting