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Manual Chapter: Load Balancing Non-Wide IP DNS Traffic to a Pool of DNS Servers
Manual Chapter
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Overview: Load balancing non-wide IP traffic to a pool of DNS servers

BIG-IP Global Traffic Manager (GTM) can function as a load balancer in front of a pool of DNS servers. In this situation, BIG-IP GTM checks incoming DNS queries and if the query is for a wide IP, load balances it to the appropriate resource. Otherwise, BIG-IP GTM forwards the DNS query to one of the servers in a pool of DNS servers, and that server handles the query.

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 load balance non-wide IP traffic to a pool of DNS servers.

Creating a pool of local DNS servers

Gather the IP addresses of the DNS servers that you want to include in a pool to which BIG-IP GTM load balances DNS traffic.
  1. Log on to the command line interface of BIG-IP GTM.
  2. Type tmsh, to access the Traffic Management Shell.
  3. Run a variation on this command sequence to create a pool using the IP addresses of the DNS servers on your network: create /ltm pool DNS_pool members add { 10.10.1.1:domain 10.10.1.2:domain 10.10.1.3:domain } monitor udp When you run the above example command, the system creates a BIG-IP LTM pool named DNS_pool that includes three DNS servers with the following IP addresses 10.10.1.1, 10.10.1.2, and 10.10.1.3. A UDP monitor is assigned to the pool to determine the availability of the pool members.
  4. Run this command sequence to save the pool: save /sys config
  5. Run this command sequence to display the pool: list /ltm pool
  6. Verify that the pool is configured correctly.

Creating a listener that alerts GTM to DNS queries for a pool of DNS servers

Configure a listener that alerts BIG-IP GTM to DNS queries destined for DNS servers that are members of a pool.
  1. Log on to the command line interface of BIG-IP GTM.
  2. Type tmsh, to access the Traffic Management Shell.
  3. Run this command sequence to create a listener: create /gtm listener DNS_listener address 192.168.5.10 ip-protocol udp pool DNS_pool translate-address enabled When you run the above example command, the system creates a listener named DNS_pool with an IP address of 192.168.5.10 that alerts BIG-IP GTM to queries destined for the members of DNS_pool.
  4. Run this command sequence to save the listener: save /sys config
  5. Run this command sequence to display the listener: list /gtm listener The system displays the new listener configuration.

Implementation results

You now have an implementation in which BIG-IP GTM receives DNS queries, load balances wide IP requests to the appropriate resource, and load balances all other DNS queries to the members of the pool of DNS servers.

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