Two types of implementations exist for DNS.
Corporate DNS, if available
Internal DDNS service transparent to the user
Cisco Unified Communications Manager Administration provides support to configure
different scopes for the DHCP server. For each scope, you can enter a range of
IP addresses and subnet masks and you can also configure options.
For configuring DNS with Corporate DNS, the corporate DNS
infrastructure is used, and default DNS configuration will act as a cache only
service to this corporate DNS service.
When no corporate DNS service exists, Dynamic Domain Name
System (DDNS) service, a service that allows dynamic updates to hostname and IP
addresses, is used to implement a clusterwide DNS infrastructure. This also
serves other devices on the network that are interacting with the cluster. Each
node has DNS running on it. These DNS servers get configured with hostname and
IP address information for all the nodes and any other devices in the cluster.
The DNS on the first node in the cluster gets configured as primary DNS, while
all other nodes get configured as secondary nodes.
When any change to DNS configuration occurs to the first node
Cisco Unified Communications Manager, the change automatically gets transferred to
other nodes. Other devices in the network can point to any of the nodes in the
cluster for the DNS lookups.
Any change to the host name of a node will require the node to be
reinserted in the cluster. Before you change the host name of a node, review
the document, Changing the IP Address and Host Name for
Cisco Unified Communications Manager Release 8.5(1).
When nodes are being configured using by DHCP, the DHCP
client on the node will get configured to dynamically update DDNS.
Whenever nodes are configured by using DHCP, one the
following events occurs:
The corporate DNS can accept dynamic updates.
DNS gets updated within the cluster
DHCP configuration for the nodes gets tied with their MAC
addresses of the node for which you are requesting an IP address. If the node
requests an IP address again, DHCP matches the MAC address to the previous
request and provides the same IP address.
You must update the DNS server with the appropriate
Cisco Unified Communications Manager name and address information before using that
information to configure the
Cisco Unified Communications Manager server.
If the AAAA record or A record do not map correctly, calls may fail.