Voice gateway

[hubertw]

Hi,
I need to participate in one project and I have no idea how to do it.
There is a LAN with working voice solution. Someone decided to put everything in one VLAN 1 - data and voice.

INTERNET------ROUTER-------CORESWITCH------ACCESSSWITCH ----workstation with management soft
VOICE GATEWAY----------------/

Today user with management soft is able to reach VOICE GATEWAY but it doesn't work after some changes.
If I add a voice vlan (on access and core), change the link between switches as trunk- the user is not able to reach VOICE GATEWAY.
Suppose that the data vlan 192.168.1.0\24 and voice vlan 172.16.1.0\24

My questions are:
- does the voice gw has two IP addresses (for management and one for communication with phones) ?
- if yes, can I configure these int with IP from different subnets ?
- does the link between coreswitch and voicegateway should be trunk or like phone interface (with data vlan and voice vlan) ?

VOICE GATEWAY - I don't know the dev, I know only that is Alcatel, no more.

Thank you for any support !
Hubert