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Manual Chapter: BIG-IP® version 9.4 Global Traffic Manager and Link Controller Implementations Guide: 2 - Delegating DNS Traffic to Wide IPs
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2

Delegating DNS Traffic to Wide IPs


Working with the Global Traffic Manager and
DNS traffic

The primary purpose of the BIG-IP® Global Traffic Manager is 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 a network must handle. Consequently, typical installations of the Global Traffic Manager involve configuring the system to work in conjunction with existing DNS servers already on the network. The recommended configuration is to configure your DNS server to delegate wide IP-related requests to the Global Traffic Manager for name resolution.

 

 

Figure 2.1 The Global Traffic Manager with 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 a delegated zone that you create on your existing DNS server.

Note

This implementation also contains recommendations for modifying the files on your existing DNS server. However, detailing how to implement these modifications is beyond the scope of this implementation. If you are unfamiliar with how to modify the files on your DNS server, we recommend you review the 5th edition of DNS & BIND, available from O'Reilly.

Delegating DNS traffic to wide IPs

This implementation describes the steps necessary to integrate a Global Traffic Manager with an existing DNS server.

This implementation focuses 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 delegated zones of www.siterequest.com, which an existing DNS server manages. They have already configured the Global Traffic Manager with two wide IPs, store.wip.siterequest.com and checkout.wip.siterequest.com, which correspond to these two web applications.

Modifying the existing DNS server

In order for the Global Traffic Manager to manage the web applications of store.siterequest.com and checkout.siterequest.com, you must create the delegated zone on the existing DNS server. Creating a delegated zone typically involves the following tasks:

  • Create an A record (address record) that defines the domain name and IP address for the Global Traffic Manager.
  • Create an NS record that defines the delegated zone for which the Global Traffic Manager is responsible.
  • Create CNAME records for each web application, which forwards requests to store.siterequest.com and checkout.siterequest.com to the wide IP addresses of store.wip.siterequest.com and checkout.wip.siterequest.com, respectively.

Again, if you are unfamiliar with how to create these zones, we recommend you review 5th edition of DNS & BIND, available from O'Reilly.

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: 192.168.5.17.

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 192.168.5.17.
  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 in which the existing DNS server manages DNS traffic unless the query is for store.siterequest.com or checkout.siterequest.com. When the DNS server receives these queries, it delegates them to the Global Traffic Manager, which then load balances them on the appropriate wide IPs.




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