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Manual Chapter: Configuring a TTL in a DNS NoError Response
Manual Chapter
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Overview: Configuring a TTL in an IPv6 DNS NoError Response

You can configure BIG-IP GTM to return IPv6 DNS NoError responses that include a TTL. This allows local DNS servers to cache the negative response. Negative caching reduces both the response time for negative DNS responses and the number of messages that must be sent between resolvers and local DNS servers.

About SOA records and negative caching

A start of authority SOA record contains a TTL that allows a local DNS server to cache a DNS NoError response to an IPv6 query.

Task summary

You can configure GTM to provide a negative caching TTL for a domain name by performing these specific tasks.

Creating a pool

Ensure that at least one virtual server exists in the configuration before you start to create a load balancing pool.
Create a pool to which the system can load balance global traffic.
  1. On the Main tab, click Global Traffic > Pools. The Pools list screen opens.
  2. Click Create.
  3. Type a name for the pool. Names must begin with a letter, and can contain only letters, numbers, and the underscore (_) character.
    Important: The pool name is limited to 63 characters.
  4. For the Health Monitors setting, in the Available list, select a monitor type, and click << to move the monitor to the Active list.
    Tip: Hold the Shift or Ctrl key to select more than one monitor at a time.
  5. For the Member List setting, add virtual servers as members of this load balancing pool. The system evaluates the virtual servers (pool members) in the order in which they are listed. A virtual server can belong to more than one pool.
    1. Select a virtual server from the Virtual Server list.
    2. Click Add.
  6. Click Finished.

Creating a wide IP that provides for negative caching

Ensure that at least one global load balancing pool exists in the configuration before you create a wide IP.
Create a wide IP configured in a manner where GTM returns an SOA record, containing a TTL with an IPv6 DNS NoError response. This allows the local DNS servers to cache the negative response, and thus provide faster responses to DNS queries.
  1. On the Main tab, click Global Traffic > Wide IPs. The Wide IP List screen opens.
  2. Click Create. The New Wide IP screen opens.
  3. From the General Properties list, select Advanced. This selection allows you to modify additional default settings.
  4. In the Name field, type a name for the wide IP.
    Tip: You can use two different wildcard characters in the wide IP name: asterisk (*) to represent several characters and question mark (?) to represent a single character. This reduces the number of aliases you have to add to the configuration.
  5. From the IPv6 NoError Response list, select Enabled. With this option enabled, the system responds faster to IPv6 requests for which it does not have AAAA records configured.
  6. In the IPv6 NoError TTL field, type the number of seconds that the local DNS servers consider the IPv6 NoError response to be valid. When you set this value, you must enable the IPv6 NoError Response setting as well.
  7. From the Pool list, select the pools that this wide IP uses for load balancing. The system evaluates the pools based on the wide IP load balancing method configured.
    1. From the Pool list, select a pool. A pool can belong to more than one wide IP.
    2. Click Add.
  8. Click Finished.

Implementation result

You now have an implementation in which GTM returns a TTL in an IPv6 DNS NoError response for a web site represented by a wide IP in the GTM configuration.

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