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Networking

Change SSH server listening IP addresses

The question - I want to make the SSH server (OpenSSH) to listen on multiple IP addresses. How do I do that? The OpenSSH server listens on port 22 on one or more IP addresses. It provides secure shell functionality to login to a remote server using SSH. The OpenSSH server can listen on one [...]

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Linux command to get IP address

Question - I need to find the IP address of my Linux machine. Is there a command that can do this on CentOS? The ifconfig command can be used to get all of the IP addresses of a Linux machine. The command can be used to get information about network adapters and their IP addresses. [...]

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The question - I need to measure the latency and throughput of my web server. Is there a Linux SSH shell commmand that I can use to do this? There is a Linux command called httping which can be used to do this very quickly! The httping command can measure the latency and throughput of [...]

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Install httping using yum

The question - I want to install the package httping on my Linux CentOS box (for web server latency and throughput measurement). When I type in httping on my shell, it says command not found. When I try to install it using yum install httping, yum is unable to find the package httping. How do [...]

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The question is - I need to know which processes are listening on port 80 on my Linux CentOS box. Is there a Linux command that can help me find this information? Yes! There are two commands, one is called netstat which is now deprecated in favor of a command called ss. Both have almost [...]

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How to use the Linux ping command?

The question was - How to use the Linux / Unix ping command to check whether a site is responding? The ping command is available on all Linux / Unix based systems as well as on Windows. The ping command sends ICMP Echo request packets to the server which then responds back with ICMP response [...]

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OpenDNS and Google Public DNS are two main publicly available free DNS services. Both provide an excellent, fast recursive DNS resolution service which also has several security features built in. Which one to use is up to you. You should try both and see which one gives you the fastest DNS service. On a Linux [...]

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The question is - how to find out which DNS servers I am using on my Windows or Linux box? DNS or domain name system is a way to convert domain names like google.com to IP addresses like 8.8.8.8. When you send a request for google.com on a web browser, the web browser asks the [...]

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Net_DNS2 is a PHP pear package which allows you to run DNS queries from PHP code. This is very useful in several situations in which you need to extract DNS records of a domain name. Net_DNS2 is compatible with both IPv6 and DNSSEC. The authors claim that Net_DNS2 is significantly faster than its precursor Net_DNS. [...]

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It is sometimes necessary to validate an IP address which is entered by a user. It is also necessary to differentiate between an IPv4 and IPv6 addresses. Detecting an IPv4 address is not that difficult, but detecting an IPv6 address is quite complicated. Fortunately, PHP has a solution which can be used to validate and [...]

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