SCP or Secure Copy securely transfers files between two hosts over the network using the SSH protocol. This tutorial explains how to use this popular command with numerous examples. SCP is pre-installed with most Linux distributions and is often used for deploying software to servers and backing up – frequently… Read More »Using the SCP Command to Securely Copy Files [Examples]
This guide explores the 500 internal server error code, an HTTP error, and how to fix it. HTTP Errors and Error Codes Whenever a web page is loaded, a request is made to an HTTP server (Most web servers run Linux, by the way), and… Read More »What Is a 500 Internal Server Error and How to Fix It?
dig is the Linux command-line tool used to look up the DNS records for a host. This tutorial explains how to use this command and includes handy examples. DNS records provide information to your computer about a host’s IP address on a network, email configuration, or… Read More »How to Use the Dig Command [With Examples]
Few will deny that monitoring of Cisco devices is essential part of sysadmin’s job. I personally use Nagios to track states of BGP neighbors on Cisco routers so if one of peers goes down I’ll receive a phone call from Nagios. You may have redundant… Read More »Track Cisco BGP peers using Nagios
Nfsen is open source sensor: it accepts netflow data from multiple netflow probes (servers, routers, vpn concentrators etc) and then visualizes it into human readable form. So using Nfsen you can see traffic statistics of every network device in your network in one place (actually Nfsen provides much more features).
By default Nfsen makes it possible to see only inbound and outbound traffic statistics but no protocol breakdown or any traffic classification. In the meantime it’s always useful to know what network applications are eating the bandwidth to understand if that fits baseline or not and take necessary actions. For example, if you’re monitoring Linux server which primary task is to host some website but in Nfsen you see that it generates 90% of SSH traffic and only 10% of web traffic then it would be reasonable idea to check if somebody is trying to brute force SSH password and stop that activity. In other words it’s better to have traffic statistics classified. In this article I’ll tell you how to enable traffic classification in Nfsen.
The Implementing Cisco IP Routing (CCNP Route 642-902). Materials for efficient preparation to the exam.
A few days ago I have successfully passed 642-902 exam (CCNP ROUTE v6) and would like to share the list of materials I have been using to prepare to that exam. To get prepared I was using official Cisco Press training resourses, lab simulations and… Read More »The Implementing Cisco IP Routing (CCNP Route 642-902). Materials for efficient preparation to the exam.
There is Cisco router of 7200 series with 4 FastEthernet interfaces (FE) and 2 serial ports. It should act as load balancer and failover for LAN connected to it via one FE 1/0 interface while two identical Internet connections are going to FE 0/0 and… Read More »Cisco Load Balancing with Failover setup example
Using nfsen it is possible to view IP traffic statistics on Linux interfaces including the graphs showing data sent and received (see the screenshot to the right) as well as historical information about all data transfers. So after you’ve configured nfsen and nfdump to monitor… Read More »Install nfdump and nfsen netflow tools in Linux
It was long time ago when I wrote here last time but today I’d like to share the link to an application that would be appreciated by everyone starting from Linux starter wishing to speed up his/her Internet connection and ending with system administrators who… Read More »Namebench: cross-platform DNS benchmarking tool
By default Cisco IOS doesn’t provide any traffic monitoring tools like iftop or iptraff available in Linux. While there are lots of proprietary solutions for this purpose including Cisco Netflow Collection, you are free to choose nfdump and nfsen open source software to monitor traffic… Read More »How to monitor traffic at Cisco router using Linux (Netflow)