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Maximum Number of Telnet Sessions Active

April 8th, 2013 | 174 Comments | Posted in network, Switch

By default, ProCurve switches support a total of three open Telnet sessions and do not automatically terminate sessions that were not properly exited.
When the maximum telnet session reached, when we try to telnet the switch, we will get a message “Sorry, the maximum number of telnet sessions are active. Try again later.”
To close the open Telnet sessions, it is necessary to either access the switch over the serial console port and kill the sessions, or else reboot.
When you access the switch through a serial console session, issue the command: “kill” at the prompt. This closes the open Telnet sessions.
To close specific telnet session, issue the command “kill <session>”. You can issue the command “show telnet” to list the telnet session.
To automatically close inactive Telnet sessions, configure an inactivity timer setting.

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Deny file/directory deletion and directory creation in vsftpd

July 6th, 2012 | 109 Comments | Posted in FTP, Linux, network

vsftpdSome times there is situation when we need users to be able to upload files to ftp server but not allowed to delete files/directories and create directory.

vsftpd have cmds_allowed directive that can be used for this purpose. In this directive, specifies a comma-delimited list of FTP commands allowed by the server.  All other commands not specified are rejected. More »

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vsftpd log files

July 6th, 2012 | 92 Comments | Posted in FTP, Linux, network

vsftpdIn vsftpd we can choose between these two log types:

– log only the file transfer (upload/download) information.

– log all FTP commands and responses. We will need this log when debugging FTP problems.

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Restrict file type with vsftpd

September 4th, 2011 | 170 Comments | Posted in FTP, Linux, network

vsftpdvsftpd have an option to restrict file type(s) for upload/download.  That vsftpd option is deny_file.  For example, to restrict file *.mp3 and *.avi, use this in vsftpd configuration file:


If we put the option in vsftpd.conf, it will be applied to all vsftpd users.  In virtual users configuration, we can put the option in specific user configuration file, so only selected user will be affected by the configuration.

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Installing and Configuring OpenVPN Server on CentOS using Webmin (part 4)

September 4th, 2011 | 249 Comments | Posted in Linux, network, Security

Configuring pfSense as OpenVPN client for site-to-site VPN


In this section, we will discuss the client side of OpenVPN site-to-site configuration. At the client side, I use pfSense as the firewall, webproxy, and VPN gateway to connect to the HO through site-to-site VPN with OpenVPN server.

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Setup time synchronization on HP Procurve switches

August 7th, 2011 | 240 Comments | Posted in network, Switch

By default, when an HP Procurve switch reboot, the switch time will revert to 1 Jan 1990 at 00:00:00. Some time, inaccurate time setting brings difficulties when we need to look at the log at a specific time. Manual time adjustments are not saved on HP Procurve switches after reboot. The solution is to setup time synchronization to a time (NTP) server. More »

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