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DNS Requirement for UC Apps


Some important considerations regarding DNS as some customers/partners frequently ask if DNS is mandatory for these apps:

For CUCM and IM&P, please check the following link

If you are using DNS in your deployment, note the following requirements:

>> Mixed-mode DNS deployments not supported—Cisco does not support mixed-mode deployments. Both Cisco Unified Communications Manager (Unified Communications Manager) and IM and Presence must either use or not use DNS.

>> If your deployment uses DNS—Unified Communications Manager and IM and Presence should use the same DNS server. If you use different DNS servers between IM and Presence and Unified Communications Manager, it is likely to cause abnormal system behavior.

>> If your deployment does not use DNS—You must modify the Host Name/IP Address field in the service profile for the Presence and IM UC service. If DNS is not supported, you must change the Host Name/IP Address field to the IP address of the IM and Presence publisher node. For more information about configuring services, see System Configuration Guide for Cisco Unified Communications Manager

>> Multinode considerations—If you are using the multinode feature in IM and Presence, see the section regarding multinode deployments in the Configuration and Administration of IM and Presence on Cisco Unified Communications Manager for DNS configuration options.

For UCCX, as per the following link:

>> DNS configuration and domain fields are mandatory for Unified CCX installation. Both forward and reverse lookups are required. DNS is required for the Unified CCX Chat feature to function and for integration with ICM by hostname in Unified IP IVR.

I will add more DNS related considerations to this doc later, suggestions from all are welcome.



Hi Manish,


The first item in the requirements states that Mixed-mode DNS deployments are not supported.  This is only referring to use of DNS on the servers, and not the use of DNS when setting the Cluster to used Mixed-mode Authentication, correct?




regarding DNS, is it possible to use different DNS domains within a CUCM cluster?

I mean Publisher in while the Subscriber in

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