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Manual Chapter: Configuring a TTL in a DNS NoError Response
Manual Chapter
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Configuring a TTL in a DNS NoError Response

Overview: Configuring a TTL in a DNS NoError Response

You can configure BIG-IP® DNS to return DNS NoError responses that include a TTL. With this configuration, local DNS servers can cache a 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 by which a local DNS server can be configured to cache a DNS NoError response to an IPv6 query.

Task summary

You can configure DNS 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 DNS > GSLB > Pools .
    The Pools list screen opens.
  2. Click Create.
  3. In the General Properties area, in the Name field, 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. From the Type list, depending on the type of the system (IPv4 or IPv6), select either an A or AAAA pool type.
  5. In the Configuration area, for the Health Monitors setting, in the Available list, select a monitor type, and move the monitor to the Selected list.
    Tip: Hold the Shift or Ctrl key to select more than one monitor at a time.
  6. In the Members area, 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.
  7. 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 BIG-IP® DNS returns an SOA record that contains a TTL with an IPv6 DNS NoError response. With this configuration, the local DNS servers can cache a negative response and thus provide faster responses to DNS queries.
  1. On the Main tab, click DNS > GSLB > Wide IPs .
    The Wide IP List screen opens.
  2. Click Create.
    The New Wide IP List screen opens.
  3. From the General Properties list, select Advanced.
  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 Type list, select a record type for the wide IP.
    Note: Once created, both the record type and name cannot be changed.
  6. From the NoError Response list, select Enabled.
    With this option enabled, the system responds faster to requests for which it does not have AAAA records configured.
  7. In the NoError TTL field, type the number of seconds that the local DNS servers consider the NoError response to be valid. When you set this value, you must enable the NoError Response setting as well.
  8. In the Pools area, for the Pool List setting, 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.
  9. Click Finished.

Implementation result

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

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