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sol277: Delegating a subdomain to a BIG-IP GTM or BIG-IP Link Controller system from another DNS server
How-ToHow-To

Original Publication Date: 02/15/2006
Updated Date: 05/07/2014

Purpose

You should consider using this procedure under the following condition:

  • When delegating subdomains from a DNS server to BIG-IP GTM or BIG Link Controller systems.

Prerequisites

You must meet the following prerequisites to use this procedure:

  • Your BIG-IP GTM or BIG-IP Link Controller system has previously been deployed with the appropriate supporting configuration.
  • You have administrative access to the Primary DNS system for your site.
  • You have a general understanding of BIG-IP GTM or BIG-IP Link Controller systems and DNS configurations.

Description

When you use a BIG-IP GTM or BIG-IP Link Controller system to provide wide area load balancing services, you may need to delegate authority for specific host names from the primary DNS server to the BIG-IP system.

Procedures

Primary DNS subdomain delegation

Complete the following steps to configure the DNS server to delegate a subdomain to the BIG-IP GTM or BIG-IP Link Controller system.

Impact of procedure: Due to the nature of DNS, F5 recommends that you perform this procedure during a maintenance window with sufficient time allotted for DNS propagation.

  1. Create a new subdomain for which the BIG-IP GTM or BIG-IP Link Controller system is authoritative.

    Make sure the subdomain contains the host names to be load balanced. In most cases, it makes sense to create a new subdomain that is used only for this purpose. For example, the subdomain name wip is often used.

  2. Delegate authority for the entire subdomain to the BIG-IP GTM or BIG-IP Link Controller system.

    On the primary DNS server, delegate authority for the subdomain to the BIG-IP GTM or BIG-IP Link Controller system by modifying the parent zone to include nameserver (NS) records for the new zone, and address (A) records for the new nameservers referenced in the NS records.

    For example, to delegate authority for the wip.domain.com subdomain to the BIG-IP GTM systems named gtm1.domain.com and gtm2.domain.com, the parent zone file should contain the following entries:

    wip IN NS gtm1.domain.com. IN NS gtm2.domain.com.
    gtm1.domain.com. IN A 192.168.101.254
    gtm2.domain.com. IN A 192.168.102.254

  3. Create an alias for each load-balanced host name to reference a host name in the delegated subdomain.
  4. On the primary DNS server, create a CNAME (Canonical Name) alias in the parent zone for the host name to be load balanced. The CNAME alias must reference a host name in the subdomain you delegated in step 2.
  5. On the BIG-IP GTM or BIG-IP Link Controller system, create a wide IP using the CNAME you just created.

    For example to have the BIG-IP GTM or BIG-IP Link Controller system load balance traffic for the www.domain.com host name, the domain.com zone should contain the following entry:

    www.domain.com. IN CNAME www.wip.domain.com

    When a client requests DNS resolution for the host name www.domain.com, the DNS server that is authoritative for the domain.com domain responds with the CNAME (alias) record www.wip.domain.com. The client then requests resolution for the host name www.wip.domain.com. Since the domain.com zone points to gtm1.domain.com and gtm2.domain.com as the authoritative nameservers for the subdomain wip.domain.com, the resolution request for www.wip.domain.com is then sent to one of the BIG-IP GTM systems. The BIG-IP GTM system responds with the most appropriate A (address) record based on the wide IP configuration.

Supplemental Information

None

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