Question

An engineer configures a Cisco UCM cluster and needs a specific IP phone line to reach both internal extensions and PSTN numbers. The phone's device-level CSS contains only the 'Internal_PT' partition, while the line-level CSS contains 'Internal_PT' and 'PSTN_PT'. A user reports the phone can call internal extensions but cannot dial any PSTN number. What is the most likely cause and correct behavior of UCM CSS processing here?

Accepted Answer

UCM concatenates the line CSS in front of the device CSS, so PSTN_PT should be searchable; the failure is caused by a different issue such as a missing route pattern or partition mismatch

Answer

UCM only evaluates the device-level CSS, so the PSTN_PT partition in the line CSS is ignored and PSTN calls fail

Answer

UCM requires the same partition to appear in both the line and device CSS before it can be used for routing, so PSTN_PT must be added to the device CSS

Answer

UCM evaluates only the device-level CSS for outbound PSTN calls and the line CSS only for internal calls, which is expected behavior