To configure products for IPv6, refer to the product configuration guides.

We recommend deploying IPv6-only device configuration where applicable, typically endpoints and PSTN gateways. All applications servers need IPv4 address and IPv6 address (dual-stack) to support all traditional IPv4 devices until all devices are IPv6-only capable including third-party products and applications.

To reduce dependency on IPv4 addresses, you can upgrade the following on-premise deployment modes to IPv6: single-site call processing deployments; multi-site distributed call-processing deployments; and multi-site deployments with centralized call processing. We recommend that you upgrade and configure:

• IPv6-only stack SIP phones, SIP gateways, and SIP trunks.

• IPv4-only stack and IPv6-only stack (dual-stack) Unified CM clusters and other application servers.

• All third-party products and applications in IPv4-only.

Department of Defense (DoD) certification requirements drove the development of Alternative Network Address Types (ANAT) RFC 4091 and 4092. ANAT allows a set of network addresses to establish a media stream is useful in environments with both IPv4-only hosts and IPv6-only hosts. For this functionality, all the devices need IPv4 address and IPv6 address assignment. ANAT was also implemented in Cisco Unified Communication System Release 7.1.2. However, since all device need both IPv4 and IPv6 addresses, ANAT does not help to reduce dependency on the now depleted number of IPv4 addresses. Based on large enterprise customer feedback, and their need for new IP addresses, ANAT SIP SDP attributes have since been deprecated by Internet Engineering Task Force (IETF).

We recommend deploying IPv6-only device configuration where applicable (typically endpoints). All servers, third-party products, and applications need IPv4 addresses and IPv6 addresses to support all traditional IPv4 devices until all devices are IPv6-only capable.