VoIP through a Firewall (NAT)

I get a lot of questions regarding VoIP equipment running behind firewalls and I know it is a common problem faced by lots of you. This causes lots of problems like one-way speach, cannot register with the GateKeeper etc.

I have listed some of the ports that you must open on your firewall to be able to start using VoIP – please note that this is far from a definitive list and certain vendors use different ports for proprietary signalling – but it should give you a head start !!

Port 23 TCP – Telnet – For CLI type functions
Port 80 TCP – HTTP – For Web browsing your gateway
Ports 161 & 162 UDP – SNMP – If you monitor your GW via SNMP
Ports 9002 & 9003 TCP – CDR – Used on a Quintum for sending the CDRs
Port 1718 UDP – RAS – Used for GateKeeper discovery
Port 1719 UDP – RAS – Used for GateKeeper registration
Port 1720 TCP – Q931 – Used for Call Signalling (Essential)
Ports 2000 to 2063 TCP – H245 – Used for H245 inter GW communication

I hope that this information proves useful and hope that people add to the list with any vendor specifics.

If you have any questions please feel free to contact me at: mhitchcock@blue-lava.co.uk

Mat.