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VoIP Firewall: Difference between revisions
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[[File:Snom710.png|link=:Category:VoIP|Go to the VoIP Category]]
=== If you are not using public IP addresses (ie NAT): ===
If your phone on private IP addresses (eg 192.168.x.x, 10.x.x.x) then you won't need to set up the firewall as you're not using pubic IP addresses.
Avoid using NAT where possible. However, some NAT gateways provide an adequate SIP ALG (e.g. Technicolor TG582), and some devices provide NAT that works with the new call server (e.g. FireBrick FB2700 and many simple NAT routers). If NAT works, then well done, but if not we cannot guarantee to be able to make it work.▼
▲Avoid using NAT where possible.
=== If you are using public IP addresses: ===
Allowing appropriate SIP and RTP packets through a firewall is the key to reliable VoIP communication. It may be possible to achieve reliability using SIP Keep-Alive packets (every 120 seconds or so) and relying on phones using UDP hole punching for the audio channel, but firewall rules are more certain to work.
This is what we suggest firewall-wise for VoIP customers who have SIP devices (phones/PABXs etc) on public IP addresses.
{| class="wikitable"
!colspan="
|-
!
!Target Ports
!Source IPs ([[IPv6]])
!Source IPs (legacy)
|-
!SIP
|UDP 5060
|2001:8b0:0:30::5060:0/112▼
2001:8b0:5060::/48▼
|81.187.30.110 - 81.187.30.119
90.155.3.0/24
90.155.103.0/24
|-
!RTP
|UDP
|2001:8b0:0:30::5060:0/112
2001:8b0:5060::/48
|81.187.30.110 - 81.187.30.119
90.155.3.0/24
90.155.103.0/24
|-''
▲|2001:8b0:0:30::5060:0/112
▲2001:8b0:5060::/48
|}
=Example FireBrick Config=
Allow inbound calls to your VoIP Phone, if you register it with FireBrick:
<syntaxhighlight lang="xml">
<rule name="Allow Firebrick" source-interface="self" comment="Allow all from the FireBrick to LAN"/>
</syntaxhighlight>
Allow inbound calls to your VoIP/Snom Phone, if you register it with Voiceless:
<syntaxhighlight lang="xml">
<rule name="SIP" source-ip="81.187.30.110-119 90.155.3.0/24 90.155.103.0/24 2001:8b0:0:30::5060:0/112 2001:8b0:5060::/48" target-ip="1.2.3.4" target-port="5060" action="accept"/>
<rule name="RTP" source-ip="81.187.30.110-119 90.155.3.0/24 90.155.103.0/24 2001:8b0:0:30::5060:0/112 2001:8b0:5060::/48" target-ip="1.2.3.4" target-port="1024-65535" protocol="17" action="accept"/>
</syntaxhighlight>
|IPv6
|UDP
|5000-
|ACCEPT
|WAN to LAN
|IPv6
|UDP
|5000-
|ACCEPT
|WAN to LAN
|IPv4
|UDP
|5000-
|ACCEPT
|WAN to LAN
|IPv4
|UDP
|5000-
|ACCEPT
|WAN to LAN
|IPv4
|UDP
|5000-
|ACCEPT
|WAN to LAN
|IPv4
|UDP
|5000-
|ACCEPT
|WAN to LAN
=NAT=
Avoid using NAT where possible. However, some NAT gateways provide an adequate SIP ALG (e.g. Technicolor TG582), and some devices provide NAT that works with the new call server (e.g. FireBrick 2500/2700 and many simple NAT routers). Using a STUN server (e.g. ''stun.aa.net.uk''
If you have 2 phones behind a NAT router, they cannot have the same SIP port number, nor the same RTP port range (if they both used port number for SIP of 5060 then when an incoming call came in to external port 5060, NAT wouldn't know which phone to send it to).
As an example with 2 phones, the first phone uses inbound SIP port 5060 and incoming RTP ports 5062-5068, and the second phone uses inbound SIP port 5040 and incoming RTP ports 5042-5048. Using iptables, the required rules would be like:
/sbin/iptables -t nat -A PREROUTING -i eth0 -m udp -p udp -s 81.187.30.112/29 --dport 5060:5069 -j DNAT --to-destination 192.168.1.12
/sbin/iptables -t nat -A PREROUTING -i eth0 -m udp -p udp -s 81.187.30.112/29 --dport 5040:5049 -j DNAT --to-destination 192.168.1.13
See: [[VoIP NAT]]
=Further VoIP Security=
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