Chapter 22 VoIP Solutions: SIP : FortiGate VoIP solutions: SIP : How the SIP ALG performs NAT : Translating SIP sessions to multiple destination ports
  
Translating SIP sessions to multiple destination ports
You can use a load balance virtual IP to translate SIP session destination ports to a range of destination ports. In this example the destination port is translated from 5060 to the range 50601 to 50603. This configuration can be used if your SIP server is configured to receive SIP traffic on multiple ports.
Figure 303: Example translating SIP traffic to multiple destination ports
To translated SIP sessions to multiple destination ports
1. Add the load balance virtual IP.
This virtual IP forwards traffic received at the port1 interface for IP address 172.20.120.20 and destination port 5060 to the SIP server at IP address 192.168.10.20 with destination port 5061.
config firewall vip
edit "sip_port_ldbl_vip"
set type load-balance
set portforward enable
set protocol tcp
set extip 172.20.120.20
set extport 5060
set extintf "port1"
set mappedip 192.168.10.20
set mappedport 50601-50603
set comment "Translate SIP destination port range"
end
2 Add a security policy that includes the virtual IP and VoIP profile.
config firewall policy
edit 1
set srcintf "port1"
set dstintf "port2"
set srcaddr "all"
set dstaddr "sip_port_ldbl_vip"
set action accept
set schedule "always"
set service "ANY"
set utm-status enable
set voip-profile default
set comments "Translate SIP destination port"
end