1. Introduction

This section is aimed to provide some further network troubleshooting information to ensure you have a successful connection to the TSM backup servers. This guide assumes that you have already followed the checks basic checks, Network Connectivity Troubleshooting Guide and/or Network Connectivity Troubleshooting Guide Stage 2.

Just to recap:

 I have internet access
I am connected to the Oxford University network (or via VPN for the VPN Backup Service)
My TSM Node is not locked
My TSM Password is not due to expire
My TSM Client is configured correctly
I can ping the required IP Address
I can ping the required Server Name

2. Troubleshooting TSM Specific Connection Part 4 - Name Resolution

Following our previous tests we have established that we have IP connectivity to the TSM Servers. However we do not have the name resolution working, which is key for TSM to work successfully.

2.1. Flushing the DNS

DNS is a naming system used by computer services to associate meaningful names to numerical identifiers (IP Addresses). Sometimes a bad DNS entry will be cached/stored on your local machine and you will need to either flush the DNS cache to remove the bad DNS entry. Follow this step-by-step process to flush the DNS:

  1. Click on Start (or the Windows Icon in Vista/Win7)
  2. Click on Run (or "Search" in Vista/Win7)
  3. Type CMD and hit Enter or click OK
  4. You should now see a command prompt screen as shown below:
    Figure 1.
  5. Using the IP Address of the Server type ipconfig /flushdns and hit Enter:
    Figure 2.
    Now review your results with those listed below:
  6. The ipconfig /flushdns command will complete and return to command prompt - the command should complete successfully:
    Figure 3.
  7. Now try to ping the servername once more as done previously
    Figure 4.
    • At the command prompt type ping servername and press Enter - where the servername relates to the server you are trying to connect to
      Figure 5.
    • You should then see the results of this ping returned and then it will return to the command prompt:
      • Successful Ping (see below)- The key here now is that the server name has resolved itself to the same IP Address that we pinged in the previous test, and having four successful "Reply from" returned.
        Figure 6.
      • Unsuccessful Ping Possibility 1 (see below) - The server name is resolving to an incorrect IP Address and returning a "timed out" message.
        Figure 7.
      • Unsuccessful Ping Possibility 2 (see below) - The server name is resolving to an incorrect IP Address but is returning successful "Reply From" responses - the key here is that the server name resolution is incorrect. If the server name is resolving to an incorrect ip address then the TSM Client will simply not work
        Figure 8.
    • If you were now able to successfully ping the server name and it resolved to the correct IP Address then please try the TSM client again. If the TSM Client is still not working you will need to start the troubleshooting process again from the beginning as the results are now different
    • If you were unable to ping the server name then please go continue to the next step

2.2. Checking the local hosts file

Whilst unlikely, there is the possibility that the local hosts file on your machine may contain an incorrect entry that will be pointing your TSM client to the incorrect servername/ipaddress. Follow these instructions to check this:

  1. Browse to the following location or your computer C:\Windows\System32\Drivers\etc
  2. Double click on the file named hosts (this file does not have file extension)
    Figure 9.
  3. You will be prompted to Open With, select Notepad and click OK
    Figure 10.
  4. A normal hosts file (like the one below) will contain some comments (marked by # at the start of the line) and a line that states 127.0.0.1 localhost
    Figure 11.
  5. If your hosts file contains further information like the one below then this may be the problem,
    Figure 12.
  6. Any line with a reference to a server name beginning with "dsm" should be commented out by putting a "#" at the start of the line, as shown below:
    Figure 13.
  7. Now select [File], [Save] and then [File], [Exit] to save the hosts file, and now try pinging the TSM Servers again.

If your hosts file was already empty of additional information or removing the additional entries has not worked then you will need to escalate this to your Local IT Support staff for further advice.