Check the voice network before an IP change

A phone may retain an address after a network change yet fail to find its call server. Check each dependency on the voice path before moving a VLAN, DHCP scope or router interface.

Record the current path

Write down the phone subnet and mask, gateway, voice VLAN, DHCP options, DNS resolvers and call-server names. Note which switch port or wireless network carries the affected devices. Save the current configuration and lease details from one working phone.

Plan a limited test

Move one test device first. Confirm it receives the intended address, resolves the call-server name, registers and completes a two-way call. Keep a rollback window long enough to account for DHCP lease and DNS cache behaviour.

Do not treat a successful ping as proof that signalling or media works. Check the whole path before expanding the change.

Refer to the IP networking reference for voice systems for address and route terms.