Identifying DNS Errors

Published : September 27, 2005

The DPM server and its protected file servers cannot communicate reliably unless DNS is functioning properly. Use the following procedures to identify and resolve DNS problems on either the DPM server or a protected file server:

• In the Services console, review the status of the following services and start them if they are not already started:

  • DNS Client

  • TCP/IP NetBIOS Helper (if the intranet is NetBIOS-enabled)

• Verify that the Hosts file exists and that the correct path to the Hosts file is configured.

  • Verify that HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ REG_EXPAND_SZ: DataBasePath is set to %SystemRoot%\System32\drivers\etc.

  • Verify that the Hosts file is located at %SystemRoot%\System32\drivers\etc\hosts.

• Empty the following caches:

  • To empty the DNS cache, run ipconfig /flushdns

  • To empty the NetBIOS cache, run nbtstat -Rand nbtstat -RR

  • To empty the Address Resolution Protocol (ARP) cache, run arp –d *

• Verify the IP addresses of the DNS servers and Windows Internet Name Service (WINS) server:

  • Run ipconfig /ALLto obtain the IP addresses.

  • Use the Pingand Tracertcommands to check network connectivity to each IP address.

• In Microsoft Management Console (MMC), open the Group Policy Object Editor snap-in for the local computer and verify the local DNS client settings in Local Computer Policy\Computer Configuration\Administrative Templates\Network\DNS Client.

• Verify DNS Suffix Search List by running ipconfig /ALL.

• Check related settings by using Network Connections in Control Panel.

  • Right-click the appropriate network connection for the LAN, and then click Properties.

  • Select Internet Protocol (TCP/IP), and then click Properties.

  • On the Internet Protocol (TCP/IP) Properties dialog box, click the Advanced button.

  • Verify the settings on DNS and WINS tabs.

• Run nslookupusing the debug and verbose options to see more detail related to the DNS queries.

• Use Network Monitor to determine whether the correct DNS server answers responds to ping.

Additional Resources

For more information on troubleshooting DNS, see:

• Domain Name System Center (https://go.microsoft.com/fwlink/?LinkId=50838)

• How DNS Works (https://go.microsoft.com/fwlink/?LinkId=50839)

• Troubleshooting DNS (https://go.microsoft.com/fwlink/?LinkId=50840)

Tools

For more information on the following tools, see TCP/IP Tools and Settings (https://go.microsoft.com/fwlink/?LinkId=50841).

• Arp: View and manage the ARP cache on the interfaces of the local computer

• Ipconfig: Display current TCP/IP network configuration values, update or release Dynamic Host Configuration Protocol (DHCP) allocated leases, and display, register, or flush DNS names.

• Nbtstat: Check the state of current NetBIOS over TCP/IP (NetBT) connections, view and update the NetBIOS name cache, and determine the names registered with WINS.

• Nslookup: Check records, domain host aliases, domain host services, and operating system information by querying DNS servers.

• Ping: Send Internet Control Message Protocol (ICMP) Echo messages to verify IP connectivity. Windows Server 2003 adds IPv6 parameters to the ping command.

• Tracert: Trace a path to a destination. Windows Server 2003 adds IPv6 parameters to the tracert command.