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Set up Vodia on Windows with two NICs and AT&T Flexible Reach


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I have a customer that gets their phone connection from an AT&T Flexible Reach router through SIP handoff. This is connected to a physical Windows 10 computer running 3CX. It's been working well but I am considering migrating to to Vodia and want to check/confirm the approach.

The customer's AT&T EdgeMarc router provides Internet from port 2 and SIP/VoIP traffic from port 8. So the Win10 computer has two NICs, one so it can get on the Internet, and one so it can get VoIP packets. The IP of the router's VoIP port is and I set up the second NIC like this:

IP address:
Subnet mask:
Default gateway:  (empty)
DNS: (empty)

More details and screen shots in this blog post:  https://www.mcbsys.com/blog/2019/02/navigating-the-mysteries-of-att-ip-flexible-reach/.

I was encouraged to see that Vodia advertises compatibility with AT&T Flexible Reach:  https://blog.vodia.com/ipflexiblereach_vodia. But I got confused when I saw that it was connecting to an IOP, which pretty clearly only has one network port. How does that even work? Do some Flex Reach configurations actually put SIP on the main LAN (the article shows the SIP IP as

Given this customer's Flex Reach configuration, will Vodia for Windows work--can I set up the Flex Reach IP to use the second NIC for VoIP traffic? Anything I need to watch out for?

Thanks for your advice.

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The PBX SIP subsystem is aware about multiple network interfaces. In a nutshell, when the PBX sends out a packet it figures out what IP address the operating system would use when sending out the packet and then puts that into the SIP/SDP message. The mechanism can be explicitly overridden by the setting for the "IP routing list". But if the operating system is configures correctly, it is all automatic. This works with IPv4, IPv6, VLAN, VPN, SD-WAN, LAN and whatever is out there. It does not matter if there are single or multiple physical addresses. Vodia IOP happens to have one physical port, but in Linux you can put many network interfaces on it. If you have a server with multiple NIC it does not make a difference for the PBX. 

Problems are mostly because of NAT, either because the SIP trunk does not use a SBC or because you want to connect users home. But if possible I would prefer to set the routing up properly on OS level and then it will be working out of the box.

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