How to monitor traffic at Cisco router using Linux (Netflow)

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 of one or many Cisco routers and get detailed monitoring data through your Linux command line or as graphs at absolutely no cost. Below is […]

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Tiny perl script for UDP flooding

Sometimes it is necessary to perform UDP flood towards some network device(s) in order to test its behavior in stress… Actually I am sure that every system administrator might use this small perl script for this purpose. Certainly there are many special programs for this but believe me that it is much more easier to do the following: 1. #touch > /tmp/flood.pl 2. #chmod +x /tmp/flood.pl 3. Copy the this […]

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Create Linux user with password

Sometimes it’s necessary to create Linux user accounts in batch mode (fully automatic) but often newbies ask how to set password for a new user without entering it manually. Thanks to heaven command useradd can get password as an input parameter, but it should be encrypted. In other words, to create Linux user account with password the following command will be useful: useradd -m -p encryptedPass username I know at […]

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CGI Perl scripts debugging (solve 500 Internal Server Error)

When you run your perl scripts in browser you would get “500 Internal Server Error” when something goes wrong. There would be several reasons of this but one thing to be done is to check if your perl script contains errors. To do it login to server you’re running perl script (I hope you use Linux ;] ) and execute command: /usr/bin/perl -w /path/to/script.cgi It will show debug information and […]

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Access to sqlite3 database through perl (script example)

By publishing this post I try to help people who want to get access to popular and simple database engine sqlite through perl script. I use sqlite to store e-mails statistics at small mail server in order to retrieve information about users’ mail activity like average response time, sent and received messages and etc. There is perl script that is used to get this data per every user or get […]

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