Dual Stack Addressing Overview
If your SIP deployment requires IPv6 addressing, you can configure Cisco Unified Communications Manager to support dual stack IPv4 and IPv6 addressing. By default, Cisco Unified Communications Manager is enabled for IPv4 addressing. At the system level, you cannot configure Cisco Unified Communications Manager to support IPv6 only because the system must still interact with devices that support IPv4 only. However, if you require IPv6 addressing, you can configure dual stack trunks and devices.
Dual Stack IPv6 at the System Level
When Cisco Unified Communications Manager is configured for dual stack addressing the system can set up calls for the following scenarios:
All devices in the call support IPv4 only
All devices in the call support IPv6 only
All devices in the call run in dual-stack mode—In this scenario, the system determines the IP address type by the configuration for the IP Addressing Mode Preference for Signaling setting for signaling events and the IP Addressing Mode Preference for Media enterprise parameter for media events.
One device supports IPv4 only and the other supports IPv6 only—In this scenario, Cisco Unified Communications Manager inserts an MTP into the call path to translate the signaling between the two addressing types.
Cisco Unified Communications Manager supports IPv6 addresses for SIP environments only. For H.323 deployments, the system inserts an MTP into the call path so that the IPv4 and IPv6 devices can communicate.
Dual Stack IPv6 for Devices
At the device level you can configure many devices and media resources such as phones, gateways, conference bridges can be configured to use IPv4 addressing only, IPv6 addressing only, or dual stack. You can configure the preferred addressing method both for signaling and for media events.
For SIP devices, you can also configure the Alternate Network Address Types (ANAT) feature allowing a registered SIP device to have both an IPv4 and IPv6 address at the same time. The device can communicate using either address type, thereby allowing the device to interoperate seamlessly in both IPv4 and IPv6 networks. You can enable ANAT for SIP devices by enabling ANAT in the SIP Profile that is assigned to the device.