Monthly Archives: March 2013

SSH Authentication by Keys

It is possible to use cryptographic keys to login to an SSH server (as an alternative to standard password authentication). I will refer to the experts on this one and send you to the CentOS wiki page for Securing SSH … Continue reading

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Quick Save of Cisco IOS Running Config

I’ve seen Cisco support use this technique over the phone a few times and think it is useful enough to post here for quick reference. The scenario is that you have terminal access (possibly via serial console) to a Cisco … Continue reading

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Cisco IOS SSH Server

Security-minded network administrators like to manage network equipment using encrypted protocols such as SSH. Cisco IOS routers and switches often require extra configuration to enable SSH. As always, refer to official Cisco IOS SSH documentation for a much more authoritative … Continue reading

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Redirect Apache Tomcat Default Page

Have you ever visited a web site at the root or base URL (no page or directory specified), only to see your browser automatically redirect to another directory or page? This can be done with a client-side html page that … Continue reading

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Text End-of-Line (EOL) Conversion

Text files do not come in a universal format. If you have ever opened a text file on Windows with Notepad and all the lines were running together – that file was probably created on a Unix or Linux system. … Continue reading

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Vim Settings

Ah the joys of classic Unix text editing! Life would not be complete without the vi editor (or vim on most Linux systems). Whether you love it or hate it, there always seems to be a time when there is … Continue reading

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RHEL 6 and CentOS 6 Email Server

Official Red Hat Enterprise Linux (RHEL) 6.x documentation for Email Servers is available in the RHEL 6 Doc – Chapter 17, Mail Servers. This information applies to CentOS 6 as well. The default MTA for SMTP service is now Postfix. … Continue reading

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Test Firewall Rules with Nmap

Nmap is an essential tool for any networking professional. It makes quick work of scanning your local network for available systems and services (text-based network mapping). For firewall administrators and security personnel, it provides excellent capabilities to check for open … Continue reading

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FTP on CentOS 6 or RHEL 6

It seems that CentOS is depending on the official RHEL documentation for version 6.x. For FTP Server configuration (vsftpd), see the official Red Hat 6.x FTP Server Document. Some hints for CentOS 6.x minimal install: Verify your configuration changes with … Continue reading

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DHCP Server in Cisco IOS

Cisco IOS provides a basic DHCP server that can be useful for testing or small networks. If you’re in an Active Directory environment I recommend providing DHCP service from your domain controller systems and using the “ip helper-address” command (dhcp … Continue reading

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