Resolving your host names

Verify that your PCs and your IBM® i platforms resolve the same host name.

Use the previous example work sheets as reference for resolving host names. To verify that the PCs and IBM i platforms are resolving the same host name for System A, follow these steps:
  1. From the PC, determine the fully qualified TCP/IP host name for System A.
    Note: Depending on how you manage your network, you might want to do this on other PCs that are joining the single sign-on environment.
    1. In Windows Explorer on the PC, open the hosts file from this location:
      • Windows XP and Windows 7 operating system: C:\WINDOWS\system32\drivers\etc\hosts
      Note: If the hosts file does not exist on the PC, then your PC might be using a DNS server to resolve host names. In that case, skip to Step 1b.

      On the work sheet, write down the first host name entry for System A, noting the uppercase or lowercase characters, for example, systema.myco.com.

      Note: If the hosts file does not contain an entry for System A, then your PC might be using a DNS server to resolve host names. In that case, see Step 1b.
    2. Use NSLOOKUP to query the DNS server.
      Note: Skip this step if you found a host name entry in the PC's hosts file, and proceed to step 2. (The hosts file takes precedence over DNS servers when the operating system resolves host names for the PC.)
      1. At a command prompt, type NSLOOKUP and press Enter. At the NSLOOKUP prompt, type 10.1.1.1 to query the DNS server for System A. Write down the host name returned by the DNS server, noting the uppercase or lowercase characters, for example, systema.myco.com.
      2. At the NSLOOKUP prompt, type systema.myco.com. This must be the host name returned by the DNS server in the previous step. Verify that the DNS server returns the IP address that you expect, for example, 10.1.1.1.
        Note: If NSLOOKUP does not return the expected results, your DNS configuration is incomplete. For example, if NSLOOKUP returns an IP address that is different from the address you entered in step 1.b.1, you need to contact the DNS administrator to resolve this problem before you can continue with the next steps.
  2. From System A, determine its fully qualified TCP/IP host name.
    1. TCP/IP domain information
      1. At the command prompt, type CFGTCP and select Option 12 (Change TCP/IP domain).
      2. Write down the values for the Host name parameter and the Domain name parameter, noting the uppercase or lowercase characters. For example:
        • Host name: systema
        • Domain name: myco.com
      3. Write down the value for the Host name search priority parameter.
        • *LOCAL - The operating system searches the local host table (equivalent of hosts file on the PC) first. If there is not a matching entry in the host table and you have configured a DNS server, the operating system then searches your DNS server.
        • *REMOTE - The operating system searches the DNS server first. If there is not a matching entry in the DNS server, the operating system then searches the local host table.
    2. TCP/IP host table
      1. At the command prompt, type CFGTCP and select Option 10 (Work with TCP/IP Host Table Entries).
      2. Write down the value in the Host Name column that corresponds to System A (IP address 10.1.1.1), noting the uppercase or lowercase characters, for example, systema.myco.com.
        Note: If you do not find an entry for System A in the host table, proceed to the next step.
    3. DNS server
      1. At a command prompt, type NSLOOKUP and press Enter. At the NSLOOKUP prompt, type 10.1.1.1 to query the DNS server for System A. Write down the host name returned by the DNS server, noting the uppercase or lowercase characters, for example, systema.myco.com.
      2. At the NSLOOKUP prompt, type systema.myco.com. This must be the host name returned by the DNS server in the previous step. Verify that the DNS server returns the IP address that you expect, for example, 10.1.1.1.
        Note: If NSLOOKUP does not return the expected results, your DNS configuration is incomplete. For example, if NSLOOKUP returns an IP address that is different from the address you entered in Step 2.c.1, you need to contact the DNS administrator to resolve this problem before you can continue with the next steps.
    4. Determine which host name value for System A to keep, based on its TCP/IP configuration.
      • If the value for the Host name search priority parameter is *LOCAL, keep the entry noted from the local host table (Step 2.b.2).
      • If the value for the Host name search priority parameter is *REMOTE, keep the entry noted from the DNS server (Step 2.c.1).
      • If only one of these sources contains an entry for System A, keep that entry.
  3. Compare the results from these steps:
    1. Step 1: The name that the PC uses for System A.
      Note: If you find an entry for System A in the PC's hosts file, use that entry. Otherwise, use the entry from the DNS server.
    2. Step 2.a.2: The name that System A calls itself within its TCP/IP configuration.
    3. Step 2d: The name that System A calls itself based on host name resolution.
    All three of these entries must match exactly, including uppercase and lowercase characters. If the results do not exactly match, you will receive an error message indicating that a keytab entry cannot be found.