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Manual Chapter: Delegating DNS Traffic to Wide IPs
Manual Chapter
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Overview: Delegating DNS traffic to wide IPs

BIG-IP Global Traffic Manager (GTM) load balances incoming wide IP traffic to your network resources. BIG-IP GTM can work in conjunction with an existing DNS server on your network. In this situation, you configure the DNS server to delegate wide IP-related requests to the BIG-IP GTM for name resolution.

Traffic flow when DNS server delegates traffic to BIG-IP GTM

This implementation focuses on the fictional company SiteRequest, which recently purchased BIG-IP GTM 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 BIG-IP GTM with two wide IPs, store.wip.siterequest.com and checkout.wip.siterequest.com, which correspond to these two web applications.

About listeners

Listeners control how BIG-IP GTM handles network traffic. A listener is a specialized virtual server that is assigned a specific IP address. A wildcard listener is a special listener that is assigned an IP address of 0.0.0.0 and DNS query port (port 53). When traffic is sent to the IP address of a listener, BIG-IP GTM either handles the traffic locally or sends the traffic to the appropriate resource.

Task summary

Perform these tasks to delegate DNS traffic to wide IPs.

Creating a delegated zone on a local DNS server

If you are unfamiliar with how to modify the files on DNS servers, review the fifth edition of DNS and BIND, available from O’Reilly Media.

Determine which DNS servers will delegate wide IP-related requests to BIG-IP GTM.

In order for BIG-IP GTM to manage the web applications of store.siterequest.com and checkout.siterequest.com, you must create a delegated zone on the existing DNS server. Perform the following steps on the selected DNS servers.
  1. Create an address record (A record) that defines the domain name and IP address of BIG-IP GTM.
  2. Create a nameserver record (NS record) that defines the delegated zone for which BIG-IP GTM is responsible.
  3. Create canonical name records (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.
A delegated zone exists on each DNS server on which you performed this procedure.

Creating a self IP address using the IP address of the legacy DNS server

Create a self IP address on BIG-IP GTM using the IP address of the legacy DNS server.
  1. On the Main tab, click Network > Self IPs.
  2. Click Create. The New Self IP screen opens.
  3. In the IP Address field, type the IP address of the legacy DNS server. The system accepts IP addresses in both the IPv4 and IPv6 formats.
  4. In the Netmask field, type the network mask for the specified IP address.
  5. Click Finished. The screen refreshes, and displays the new self IP address in the list.

Designating GTM as the primary server for the zone

Ensure that you have created a self IP address on BIG-IP GTM using the IP address of the legacy DNS server.
Add the new self IP address to the BIG-IP GTM server object. Then modify the DNS server based on your network configuration.
  1. Log on to BIG-IP GTM.
  2. On the Main tab, click Global Traffic > Servers. The Server List screen opens.
  3. Click the name of the BIG-IP GTM system that you want to modify. The server settings and values display.
  4. In the Address List area, add the new self IP address.
  5. Click Update.
  6. Do one of the following based on your network configuration:
    • Modify the IP address of the legacy DNS server so that it becomes a secondary DNS server to BIG-IP GTM. Ensure that the IP address of the DNS server does not conflict with the self IP address that you added to the BIG-IP GTM server object.
      Note: If you are unfamiliar with how to change a DNS server from a primary to a secondary, refer to the fifth edition of DNS and BIND, available from O’Reilly Media.
    • Remove the legacy DNS server from your network.
BIG-IP GTM is now the authoritative name server for the zone. The root servers for the zone do not need to be updated, because the IP address of the legacy DNS server was added to BIG-IP GTM.

Creating a listener to handle traffic for wide IPs

You need to create a listener that corresponds to a delegated zone that you create on your existing DNS server. This listener will identify DNS traffic that is destined for BIG-IP GTM.
  1. On the Main tab, click Global Traffic > Listeners . The Listeners List screen opens.
  2. Click Create. The new Listeners screen opens.
  3. In the Destination field, type the IP address on which BIG-IP GTM listens for network traffic. The destination is a self IP address on BIG-IP GTM.
  4. From the VLAN Traffic list, select All VLANs.
  5. From the Protocol list, select either UDP or TCP.
  6. Click Finished.

Implementation results

You now have an implementation of BIG-IP GTM in which a DNS server manages DNS traffic unless a query is for a wide IP configured on BIG-IP GTM. When the DNS server receives queries for store.siterequest.com or checkout.siterequest.com, it delegates the queries to BIG-IP GTM, which then load balances the traffic to the appropriate wide IPs.

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