The nmap utility can identify a number of operating systems based on their fingerprints if the fingerprints are contained in the nmap database of known operating ~]# nmap -A ocfs2-2Ģ2/tcp open ssh OpenSSH 5.3 (protocol 2.0) You can verify you have the correct node by looking at its running services and its OS fingerprint. In example shown in Listing 3, we are verifying that the ocfs2-2 node is actually the node we are looking for. Have you ever had a situation in which you could contact a host but were not sure you were communicating with the correct host or using the correct IP address? The nmap utility is a very powerful tool for network scanning and diagnostics, and it can provide exactly that information. Example of output from the mtr application Figure 1 shows an example of the output from the cloud instance to the same popular search engine used in the Listing 2.įigure 1. The mtr application can provide real-time data about latency and routing changes for end users. ( mtr stands for My Traceroute, although it originally stood for Matt's Traceroute because the application was written by Matt Kimball in 1997.) A very useful application for looking at network latency is mtr. Example of using the traceroute utilityīoth ping and traceroute are quite useful on their own, but in a lot of cases, they can provide only limited information based on a short duration of time. The IP address of the cloud instance has been replaced with x.x.x.x in this ~]$ traceroute The example shown in Listing 2 uses traceroute to trace the path to a popular search engine from the demo cloud instance. The traceroute application can show us the path that packets are taking to reach their destination. Many networks are quite complicated, and packets move through many different layers of routing and switching equipment to reach the intended destination. If one of the packets had an abnormally long reply time, that might be an indicator of some type of network congestion or issue. The ping command can also be used to identify network latency issues. It was sent six ICMP packets and responded to all of them and had an average response time of 0.218ms. In the output shown in Listing 1, you can see that test2 is responding. The ping application will continue to run until you terminate it by pressing ~]# ping test2 In the example shown in Listing 1, we are going to ping the test2 system from the test1 system to see whether test2 responds on the network. The ping application is a simple utility that sends an Internet Control Message Protocol (ICMP) packet to a remote host on your network to see whether you get a reply. The most basic test you can perform to determine network connectivity is the ping test. This article will help solve some of the mystery and make network connectivity a bit more user friendly. The reality is that you can actually see what's going over the wire, and there are a number of tools built into Oracle Linux for troubleshooting network issues. Despite advances in modern operating systems, many users believe there is no way to directly "see" what's going over the wire, and that often leads to confusion and difficulties when something goes wrong. When applications that use network connectivity for communication are not working, the cause is often a mystery. Use built-in Oracle Linux tools to troubleshoot network connectivity problems.
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