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Manual Chapter: BIG-IP® version 9.4 Global Traffic Manager and Link Controller Implementations Guide: 3 - Replacing a DNS Server with the Global Traffic Manager
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3

Replacing a DNS Server with the Global Traffic Manager


Working with the Global Traffic Manager and
DNS traffic

The primary purposes of the Global Traffic Manager are to help you manage incoming wide IP traffic, and load balance that traffic to the appropriate network resources. However, wide IP traffic is only part of the overall DNS traffic that a network must handle. One implementation of the Global Traffic Manager has the system become the authoritative name server for both wide IPs and all other DNS-related traffic. Typically, this implementation requires that the Global Traffic Manager replace an existing DNS server on the network.

 

 

Figure 3.1 The Global Traffic Manager replacing an existing DNS server

To control how the Global Traffic Manager responds to DNS requests, you must configure a listener. A listener is a specialized resource that is assigned a specific IP address and uses port 53, the DNS query port. When traffic is sent to that IP address, the listener alerts the Global Traffic Manager, allowing it to handle the traffic locally or forward the traffic to the appropriate resource.

In this configuration, you must create a listener that corresponds to the IP address of the Global Traffic Manager. Since the Global Traffic Manager replaces an existing DNS server, this IP address must correspond with the IP address denoting the authoritative name server for the appropriate domain.

Note

The steps in this solution assume that you understand BIND and CNAME records. If you are unfamiliar with these topics, we recommend you review the 5th edition of DNS & BIND, available from O'Reilly.

Replacing a DNS server with the Global Traffic Manager

This solution covers the steps necessary to replace an existing DNS server with the Global Traffic Manager. In this solution, the existing DNS server has an IP address of 192.168.5.73, while the Global Traffic Manager has an IP address of 192.168.10.105.

Here, the focus is on the fictional company SiteRequest. SiteRequest recently purchased a Global Traffic Manager to help load balance traffic across two of its web-based applications: store.siterequest.com and checkout.siterequest.com. These applications are subdomains of www.siterequest.com, which are managed by an existing DNS server. SiteRequest has decided to replace its existing DNS server with the Global Traffic Manager. Earlier, SiteRequest configured the wide IPs that it needs on the system; the final task is to make the Global Traffic Manager the authoritative name server for our domains.

The tasks you must complete to replace a DNS server with the Global Traffic Manager are:

  • Configure the DNS server for zone transfers
  • Acquire a hint zone file
  • Enable recursive queries
  • Acquire zone files
  • Designate the Global Traffic Manager as the primary DNS server
  • Configure a listener

Configuring the DNS server for zone transfers

Before you configure the Global Traffic Manager to replace the existing DNS server, you need to configure the DNS server to allow zone file transfers to the Global Traffic Manager. You can enable this authorization through the use of an allow-transfer statement that specifies the IP address of the Global Traffic Manager: 192.168.10.105. Please refer to your BIND documentation for more information on how to implement an allow-transfer statement.

Acquiring a hint zone file

Another task you must accomplish before the Global Traffic Manager becomes the primary DNS server is to acquire a hint zone file. By default, the Global Traffic Manager does not include a root hints file, which contains information on the name servers for the root zone. The Global Traffic Manager must have this file to process recursive DNS queries.

You can add this file to the Global Traffic Manager through the ZoneRunner™ utility, using one of two methods:

  • Load the file from another system.
  • Transfer the file from the existing DNS server.

Loading the hint file from another system

If you want to update the hint file that you use to track the locations of the name servers for the root zone, you must first download a new hint file to your local system. Once you have the file, you can load it into the Global Traffic Manager using the ZoneRunner utility.

To load the hint file

  1. On the Main tab of the navigation pane, expand Global Traffic and then click ZoneRunner.
    The main ZoneRunner screen opens.
  2. On the menu bar, click Zones.
    The main Zones screen opens.
  3. Click the Create button.
    The New Zones screen opens.
  4. From the View list, select external.
    The external view is a default view to which you can assign different zones.
  5. In the Name box, type the name of the file.
    In this example, type Root.
  6. From the Zone Type list, select Master.
  7. From the Records Creation Method, select Load From File.
  8. In the Zone File Name box, type the name of the zone file.
    In this sample, type named.root.
  9. In the Upload Records File box, type the path to the root hints file.
    Alternatively, you can click the Browse button to navigate to the file.
  10. Click the Finished button.

Transferring the hint file from the existing DNS server

An alternative method of acquiring the hint file is to use the hint file that exists on the existing DNS server. This option is appropriate if you decided that you did not need a newer version of the file.

To transfer the hint file from the existing DNS server

  1. On the Main tab of the navigation pane, expand Global Traffic and then click ZoneRunner.
    The main ZoneRunner screen opens.
  2. On the menu bar, click Zones.
    The main Zones screen opens.
  3. Click the Create button.
    The New Zones screen opens.
  4. From the View list, select external.
    The external view is a default view to which you can assign different zones.
  5. In the Name box, type the name of the file.
    In this example, type Root.
  6. From the Zone Type list, select Master.
  7. From the Records Creation Method, select Transfer from Server.
  8. In the Zone File Name box, type the name of the zone file.
    In this sample, type named.root.
  9. In the Source Server box, type the IP address of the existing DNS server.
    In this example, type 192.168.5.73.
  10. Click the Finished button.

Enabling recursive queries

After you add the root hint file to the Global Traffic Manager, you can enable the system to process recursive queries.

To enable recursive queries

  1. On the Main tab of the navigation pane, expand System and then click General Properties.
    The General Properties screen opens.
  2. From the Global Traffic menu, choose General.
    The general global properties screen opens.
  3. Enable the Gtmd Sets Recursion option.
  4. Click the Update button to save your changes.

The Global Traffic Manager can now process the queries it receives as recursive queries.

Acquiring zone files

The next task you must accomplish before the Global Traffic Manager becomes our primary DNS server is to acquire the siterequest.com zone files from the existing DNS server. Again, this task requires that you have added an allow-transfer statement to the existing DNS server that authorizes zone transfers to the Global Traffic Manager. You can acquire these zone files through the ZoneRunner utility.

To acquire zone files

  1. On the Main tab of the navigation pane, expand Global Traffic and then click ZoneRunner.
    The main ZoneRunner screen opens.
  2. On the menu bar, click Zones.
    The main Zones screen opens.
  3. Click the Create button.
    The New Zones screen opens.
  4. From the View list, select external.
    The external view is a default view to which you can assign different zones.
  5. In the Name box, type the name of the zone file.
    In this example, type siterequest.com.
  6. From the Zone Type list, select Master.
  7. From the Records Creation Method, select Transfer from Server.
  8. In the Zone File Name box, type the zone file name.
    In this example, type db.siterequest.com.
  9. In the Source Server box, type the IP address of the existing DNS server.
    In this example, type 192.168.5.73.
  10. Click the Finished button.

Designating the Global Traffic Manager as a primary DNS server

At this point, you have configured the Global Traffic Manager as the primary (master) DNS server for the siterequest.com zone. You must now either change the existing DNS server to become a secondary (slave) DNS server to the Global Traffic Manager, or remove it from your network.

Note

Please refer to your BIND documentation if you are unfamiliar with how to change a DNS server from a primary DNS server to a secondary DNS server.

Configuring a listener

The final configuration step requires you to set a listener on the Global Traffic Manager. The Global Traffic Manager employs this listener to identify the DNS traffic for which it is responsible. In this solution, the listener you create is the same as the IP address of the Global Traffic Manager: 192.168.5.73.

To configure the listener

  1. On the Main tab of the navigation pane, expand Global Traffic and then click Listeners.
    The main Listeners screen opens.
  2. Click the Create button.
    The New Listener screen opens.
  3. In the Destination box, type the IP address on which the Global Traffic Manager listens for network traffic.
    In this example, the IP address you add is 192.168.5.73.
  4. From the VLAN Traffic list, select All VLANs.
  5. Click the Finished button to save the new listener.

You now have an implementation of the Global Traffic Manager that is now also the authoritative name server for siterequest.com. This system now handles any incoming DNS traffic, whether destined for a wide IP or another node of siterequest.com.




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