Managing Dynamic Domains

 

Dynamic DNS (DDNS)

In DNS, a zone is a portion of the domain namespace, and the ability to create new zones dynamically is very essential, especially in environments where zones need to be added or removed without manual intervention. Dynamic DNS (DDNS) can be enabled for various types of zones where it is necessary to dynamically update DNS records without manual intervention. Here are the types of zones where DDNS can be enabled:

  1. Primary Zones:
    • DDNS is most commonly enabled on primary zones. In a primary zone, the DNS records are stored and managed directly on the authoritative DNS server.
    • With DDNS, clients such as DHCP servers or DHCP clients can add, remove, or update DNS records in the primary zone dynamically. This is often used for automatically updating the DNS records of hosts as they obtain IP addresses from a DHCP server.
  2. Secondary Zones:
  • While DDNS updates are not directly applied to secondary zones, secondary zones can receive updates indirectly via zone transfers from the primary zone.
  • When a DDNS update is made to the primary zone, the updated information is propagated to the secondary zones through the standard zone transfer mechanism (AXFR).
  • Reverse Zones:
    • A reverse domain needs Dynamic DNS (DDNS) for several reasons, mainly related to the management of changing IP addresses and the need to maintain accurate reverse DNS records.

    Enabling DDNS in DDI Central

    To enable your DHCP server to dynamically provision IP address to your domains:

    • When creating a domain via Domains -> Add Domain, enable DDNS and assign a TSIG key for secure dynamic updates. If DDNS is not enabled at this stage, it cannot be activated later through the DNS menu.
    • Alternatively, add domains that require dynamic configurations by navigating to DHCP -> Domains.
    • On the Domains page, Click on the Add Domain button in the top right corner.

    • Note: For your DHCP server to provision network parameters like IP addresses to your domains make sure your Domains and DHCP server are in the same network address.

    Dynamic authoritative zones

    Dynamic DNS (DDNS) allows the automatic updating of a DNS record when an IP address changes. This is often used for hosts with dynamic IP addresses assigned by a DHCP server.

    Forward Mapping Dynamic Zones

    To create a dynamic Forward Mapping Authoritative Zone:

    • Enable DDNSfor the zone via one of the methods discussed above This would automatically enable the following DHCP options for the domain: ddns-updates:true, ddns-update-style:interim, domainname
    • Now select the subnet that you would like to provision IP addresses to the domain. Within that subnet specify the option domainname and specify the domain name you would like to create hosts to via dynamic updates like: domainname: data.com. This would enable the specific subnet to provision ip address to the hosts of that particular domain. Save the configurations.
    • Now for an authoritative forward mapping zone, enabling DDNS would automatically create an A record with a host name assigned to it. the host name assumes variable IPs provisioned by the chosen subnet.
    • Example: In the provided example, ip6.com. is an IPv6 based Forward mapping zone. Upon enabling DDNS, the DNS server will automatically generate a AAAA record for the zone. Within the AAAA record you can find the host name that holds dynamically variable IPv6 address provisioned by the DHCP server.

      • Reverse dynamic Zones

      For an authoritative reverse mapping zone, enabling DDNS will automatically generate PTR records that correspond to the hostnames within the authoritative A (or AAAA) records of a forward mapping zone.

      Example: In the provided example, 1.1.1.in-addr.arpa. is an IPv4-based reverse zone. Upon enabling DDNS, the DNS server will automatically generate a PTR record within this reverse zone. These PTR records will correspond to the hostnames defined in the authoritative A records of the forward-mapping zone.

      The PTR record's name is the reverse of the IPv4 address appended to in-addr.arpa.

      The reverse zone name 1.1.1.in-addr.arpa. would be the reverse of the assigned IPv4 address and the corresponding PTR record within that zone points to host.check.com. which is the hostname of the system that was assigned the IPv4 address. This enables reverse DNS lookups, where querying the IPv4 address in reverse notation returns the hostname host.check.com.

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