Hi Yancy,
Using IP addresses vs DNS is a supported method of configuration
Domain Name System (DNS)
DNS enables the mapping of host names and network services to IP addresses within a network or networks. DNS server(s) deployed within a network provide a database that maps network services to hostnames and, in turn, hostnames to IP addresses. Devices on the network can query the DNS server and receive IP addresses for other devices in the network, thereby facilitating communication between network devices.
Complete reliance on a single network service such as DNS can introduce an element of risk when a critical Unified Communications system is deployed. If the DNS server becomes unavailable and a network device is relying on that server to provide a hostname-to-IP-address mapping, communication can and will fail. For this reason, in networks requiring high availability, Cisco recommends that you do not rely on DNS name resolution for any communications between Unified CM and the Unified Communications endpoints.
For standard deployments, Cisco recommends that you configure Unified CM(s), gateways, and endpoint devices to use IP addresses rather than hostnames. For endpoint devices, Cisco does not recommend configuration of DNS parameters such as DNS server addresses, hostnames, and domain names. During the initial installation of the publisher node in a Unified CM cluster, the publisher will be referenced in the server table by the hostname you provided for the system. Before installation and configuration of any subsequent subscribers or the definition of any endpoints, you should change this server entry to the IP address of the publisher rather than the hostname. Each subscriber added to the cluster should be defined in this same server table via IP address and not by hostname. Each subscriber should be added to this server table one device at a time, and there should be no definitions for non-existent subscribers at any time other than for the new subscriber being installed.
During installation of the publisher and subscriber, Cisco recommend that you do not select the option to enable DNS unless DNS is specifically required for system management purposes. If DNS is enabled, Cisco still highly recommend that you do not use DNS names in the configuration of the IP Communications endpoints, gateways, and Unified CM servers. Even if DNS is enabled on the servers in the cluster, it is never used for any intra-cluster server-to-server communications and is used only for communications to devices external to the cluster itself.
Cisco Unified CM 5.0 and later releases do not permit the manual configuration of HOSTS or LHOSTS files. A local version of the HOSTS table is automatically built by the publisher in each cluster and distributed to all subscriber nodes via a secure communications channel. This local table is used for managing secure intra-cluster communications and does not contain addresses or names of any endpoints other than the Unified CM servers themselves. LMHOSTS files do not exist and are not used by Cisco Unified CM 5.0 and later releases.
http://www.ciscosystems.net.mu/en/US/docs/voice_ip_comm/cucm/srnd/7x/netstruc.html#wpmkr1043811
Hope this helps!
Rob
Please support CSC Helps Haiti
https://supportforums.cisco.com/docs/DOC-8895
https://supportforums.cisco.com/docs/DOC-8727
