The network configuration includes enabling the SIP Traffic option on the internal and
wan1 interfaces. You must enable SIP traffic on these interfaces to accept and process
SIP calls. No other special network configuration, firewall policies, or routing is required
for the FortiGate Voice to accept and process SIP calls.

This example also describes how to configure the FortiGate Voice as a DHCP server
and DNS server for the branch office internal network. As a DHCP server the FortiGate
Voice can supply network configuration settings for the PCs and FortiFones on the
internal network.

3 Configure network settings for the PCs on the Internal network.
4 Configuring the FortiGate Voice PSTN and PBX settings.

Branch Office

Internal network

PCs with SIP soft phones

and FortiFones

Subnet: 172.20.120.0

Extension Range 6000 - 6999

FortiFone

behind a NAT

device

NAT device

WAN

fxo1

Head Office

IP: 192.168.30.10

Extention Range

2000 - 2999

VoIP Provider

IP: 192.168.20.10

Remote Users

with FortiFones or

SIP soft phones

Extension range

6000 - 6999

PSTN

Remote

FortiGate unit

in NAT mode

SIP Trunking

LAN

internal

172.20.120.10

wan1

192.168.10.10

external

192.168.40.10

SIP

a/b - wire

FortiGate Voice-80C

Internet

Note: You do not have to add SIP firewall policies to enable SIP traffic for the FortiGate
Voice unit to function as a PBX. Also, with PBX functionality enabled, you cannot apply
FortiGate SIP application control features to SIP traffic received by FortiGate Voice
interfaces for which you have enabled the SIP Traffic option.