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Manual Chapter: Configuring a TTL in a Return Code On Failure
Manual Chapter
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Overview: Configuring a SOA Negative Caching TTL in a Return Code on Failure

You can configure BIG-IP® DNS to return a start of authority (SOA) Negative Caching time-to-live (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 Return Code On Failure to a 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 with an applicable pool type

Ensure that at least one virtual server or wide IP exists in the configuration before you start to create a load balancing pool.
Create a pool in order to configure the BIG-IP® system to load balance global traffic.

Creating a pool with pool type A or AAAA

Create an A or AAAA pool type in order to configure the BIG-IP® system to load balance global traffic.
  1. On the Main tab, click DNS > GSLB > Pools .
    The Pool 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 Load Balancing Method setting, from the Preferred List, select Round Robin.
    Tip: When deploying this implementation in a lab environment, to determine whether the BIG-IP® system returns the DNS response that you expect, try selecting the Global Availability method and disabling the first pool member in the list.
  7. From the Alternate and Fallback lists, select a static load balancing method, based on your network environment. Ensure that you select a load balancing method that does not take current server performance or connection load into account.
  8. 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.
  9. Click Finished.

Creating a pool with pool type NAPTR

Create an NAPTR pool type in order to configure the BIG-IP® system to load balance global traffic.
  1. On the Main tab, click DNS > GSLB > Pools .
    The Pool 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, select the NAPTR type.
  5. In the Members area, for the Load Balancing Method setting, from the Preferred List, select Round Robin.
    Tip: When deploying this implementation in a lab environment, to determine whether the BIG-IP® system returns the DNS response that you expect, try selecting the Global Availability method and disabling the first pool member in the list.
  6. From the Alternate and Fallback lists, select a static load balancing method, based on your network environment. Ensure that you select a load balancing method that does not take current server performance or connection load into account.
  7. In the Members area, for the Member List setting, from the Flags list, select a flag.
  8. Add wide IPs as members of this load balancing pool.
    The system evaluates the wide IPs (pool members) in the order in which they are listed. A wide IP can belong to more than one pool.
    1. From the Wide IP list, select a wide IP or type a name that matches an existing wildcard wide IP.
    2. In the Service field, type the name of a service or protocol.
    3. Click Add.
  9. Click Finished.

Creating a pool with pool type SRV

Create a SRV pool type in order to configure the BIG-IP® system to load balance global traffic.
  1. On the Main tab, click DNS > GSLB > Pools .
    The Pool 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, select the SRV type.
  5. In the Members area, for the Load Balancing Method setting, from the Preferred List, select Round Robin.
    Tip: When deploying this implementation in a lab environment, to determine whether the BIG-IP® system returns the DNS response that you expect, try selecting the Global Availability method and disabling the first pool member in the list.
  6. From the Alternate and Fallback lists, select a static load balancing method, based on your network environment. Ensure that you select a load balancing method that does not take current server performance or connection load into account.
  7. Add wide IPs as members of this load balancing pool.
    The system evaluates the wide IPs (pool members) in the order in which they are listed. A wide IP can belong to more than one pool.
    1. In the Members area, for the Member setting, from the Wide IP list, select a wide IP or type a name that matches an existing wildcard wide IP.
    2. In the Port field, type a port number.
    3. Click Add.
  8. Click Finished.

Creating a pool with pool type CNAME

Create a CNAME pool type in order to configure the BIG-IP® system to load balance global traffic.
  1. On the Main tab, click DNS > GSLB > Pools .
    The Pool 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, select the CNAME type.
  5. In the Members area, for the Load Balancing Method setting, from the Preferred List, select Round Robin.
    Tip: When deploying this implementation in a lab environment, to determine whether the BIG-IP® system returns the DNS response that you expect, try selecting the Global Availability method and disabling the first pool member in the list.
  6. From the Alternate and Fallback lists, select a static load balancing method, based on your network environment. Ensure that you select a load balancing method that does not take current server performance or connection load into account.
  7. Add wide IPs as members of this load balancing pool.
    The system evaluates the wide IPs (pool members) in the order in which they are listed. A wide IP can belong to more than one pool.
    1. In the Members area, for the Member setting, from the Wide IP list, select a wide IP or type a name that matches either an existing wildcard wide IP or wide IP alias.
    2. If necessary, to allow the member to point to a name that does not exist as a wide IP on DNS, select the Static Target check box.
    3. Click Add.
  8. Click Finished.

Creating a pool with pool type MX

Create a MX pool type in order to configure the BIG-IP® system to load balance global traffic.
  1. On the Main tab, click DNS > GSLB > Pools .
    The Pool 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, select the MX type.
  5. In the Members area, for the Load Balancing Method setting, from the Preferred List, select Round Robin.
    Tip: When deploying this implementation in a lab environment, to determine whether the BIG-IP® system returns the DNS response that you expect, try selecting the Global Availability method and disabling the first pool member in the list.
  6. From the Alternate and Fallback lists, select a static load balancing method, based on your network environment. Ensure that you select a load balancing method that does not take current server performance or connection load into account.
  7. Add wide IPs as members of this load balancing pool.
    The system evaluates the wide IPs (pool members) in the order in which they are listed. A wide IP can belong to more than one pool.
    1. In the Members area, for the Member setting, from the Wide IP list, select a wide IP or type a name that matches an existing wildcard wide IP.
    2. Click Add.
  8. 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 a Return Code On Failure response. With this configuration, the local DNS servers can cache a negative response and 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 one of these record types for the wide IP:
    Option Description
    NAPTR The Name Authority Pointer record, NAPTR, aids in the standardization of Uniform Resource Names (URNs). NAPTR records map between sets of URNs, URLs and plain domain names, and suggest to clients the protocols available for communication with the mapped resource.
    A The Address record, or A record, lists the IP address for a given host name.
    SRV The Service resource record, SRV, is a pointer with which an alias for a given service is redirected to another domain.
    CNAME The Canonical Name resource record, CNAME, specifies an alias or nickname for the official, or canonical, host name.
    AAAA The IPv6 Address record, or AAAA record, lists the 128-bit IPv6 address for a given host name.
    MX The Mail Exchange resource record, MX, defines the mail system(s) for a given domain.
  6. From the Return Code On Failure list, select Enabled.
  7. From the RCODE list, select one of these options:
    Option Description
    NOERROR (No Error) No error condition.
    FORMERR (Query Format Error) The name server was unable to interpret the query.
    SERVFAIL (Server Failure) The name server was unable to process this query due to a problem with the name server.
    NXDOMAIN (Non Existent Domain) The domain name referenced in the query does not exist.
    NOTIMP (Not Implemented) The name server does not support the requested kind of query.
    REFUSED (Refuse To Answer) The name server refuses to perform the specified operation for policy reasons.
  8. In the SOA Negative Caching TTL field, type the number of seconds that the local DNS servers consider the Return Code On Failure to be valid.
  9. 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.
  10. Click Finished.

Implementation result

You now have an implementation in which DNS returns a TTL in a Return Code On Failure for a web site represented by a wide IP in the BIG-IP DNS configuration.

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