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Home > AS/400 Tips > iSeries administrator tips > How to use NETSTAT to troubleshoot your iSeries network connections |
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ISERIES ADMINISTRATOR TIPS How to use NETSTAT to troubleshoot your iSeries network connectionsDan Reusche 10.13.2005 Rating: -4.44- (out of 5)
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Another option that allows you to quickly focus on the connections of interest is F15 (Shift+F3), the subset function, which is shown in Figure 4. This screen allows you to put in specific IP addresses or ports -- or a range of addresses and ports. According to the help text, you can "speci
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fy either a specific single value or a numeric range for any combination of local Internet address, local port number, remote Internet address, and remote port number." So, if you know the local or remote address for the connection in which you are interested, you can quickly zoom in on it.
Let's take an example. Suppose we have a Web server configured at address 11.222.33.44, and this Web server talks to a back-end server at another address in our network using port 1234. Perhaps we want to see all the connections between the two systems that are currently active. We can subset the list by using F15 and entering the information as shown in Figure 4.
Figure 4. An example of the subset function
When we press Enter, we will see the subsetted list of connections that are currently active. Now let's use another function key, F11, to display the actual byte counts on the various connections in our subsetted list. It may look something like the screen shown in Figure 5.
Figure 5. NETSTAT F11 -- Display byte counts
You could then use F13 to sort the list by the number of bytes into the connection.The sort is always ascending, so if we wanted to see the busiest connection, we would scroll to the bottom of the list. We can then use option 8 against the busiest job to display the iSeries job associated with this connection. We can also use F5 (Refresh) to see how quickly the byte counts are changing. By displaying the byte counts and using F5, we can verify that traffic is actually flowing on the connection, which can be a helpful debug aid.
NETSTAT, and particularly the *CNN option, can give you a lot of information, presented in a variety of ways. If you use TCP/IP connections, you will quickly discover that this is one of the best tools in your toolbox.
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About the author: Dan Reusche is a senior systems administrator at Think Federal Credit Union in Rochester, Minn. He has worked with the IBM AS/400 and iSeries platform since 1988, when he worked at the IBM Rochester Development Lab and support of AS/400 systems used within IBM. You may contact him at dreusche@chartermi.net. |
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