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Binding to IPv4 address


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I have been setting up a new snomONE PBX today on a debian server. The server has multiple addresses mapped onto alias interfaces within the operating system. I have been in and configured Settings > ports > Bind to specific IP address (IPv4):


Im running Delta Aurigids is one of the aliased IP's on the server but not the primary IP. is the main IP of the server.


From looking at traffic flows the RTP traffic is being bound to the address but any other traffic originating from the PBX is being originated at


I need all traffic to be originating from and not just the RTP traffic.


Is there any way of doing this?


Thanks in advance



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Binding to IP addresses is a good way to use multiple cores and at the same time allowing users to use the same port 5060 on different IP addresses. For TCP this is relatively easy, because TCP sticks to the local address that was used when connecting to the socket. This does solve a big problem as long as users can use TCP or TLS for SIP.


With SIP/UDP, things are more complicated. If you bind a socket to an IP address, the outbound traffic should actually also come from that IP address. Here it is important that the routing table (operating system level) has the necessary entries for that.


For media, the PBX does not bind to a specific IP address by default. However there is a settings called "Bind to specific IP address (IPv4)" where you can specify what IP address the PBX should bind RTP ports to.

The other workaround is to use different ports than 5060 for each instance. Ports can be "advertised" by DNS SRV if you use domain names. Then you don't even need multiple IP addresses.

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Oh other ports are much more flexible than rtp. you can use a list of space-separated addresses like " [::1]:5050" on SIP UDP, TCP, TLS and HTTP TCP, TLS and also on TFTP ports. It would read as "bind a socket to address on port 5060, then another one on port 5060 and another one on ::1 (the IPv6 loopback address) on port 5050. See http://wiki.snomone.com/index.php?title=Ports for some more information.

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