1 x LAN, 2 x ISPs (1 SIP, 1 Other traffic) - Brain ache

Small site with 15 users, Win server 2012 running happily (DHCP, DNS etc) and Win 7 client PCs.

They have a high speed Fibre connection for normal traffic (Internet, email etc). they will have a dedicated Voice “approved” ADSL line for SIP traffic.


Can is “simply” add the second router/default gateway and just point freePBX at it? i.e. leave the rest of the LAN, phones included, to use the “normal” lan for their network needs (DG, DNS, DHCP etc). thus, the phones know where to find the freePBX box (via their TFTP derived config files), so dont’ need to know about the second gateway, the freePBX box knows how to get to the outside world as its hard wired to the 2nd ISP/Default gateway.

DNS for ALL devices is dealt with by the Wintel server… (freePBX is on a static IP internally and listed in teh DNS of the Wintel box)

Am I missing something? I’m not aiming for HA or failover etc, just putting the SIP traffic on one external connection and everything else on the other.

(Other options could be VANS as all kit on site supports it, though not sure how this affects pass through traffic if a device attaches to the back of the phone…?)

Ta in advance!


In dual homes systems I install I usually make the default route out the Internet and point routes back to the customers network.

Hi alan, not sure I follow…

are you saying leave the default route for all traffic via the existing/working router/ISP and then have incoming only on the dedicated router/ISP?

Here’s a little diagram of what I envisage:

Current router: - Its the default gateway and does NAT to the outside world, all traffic except SIP.

New Router: - dedicated to SIP traffic, Internal DNS:

Wintel box: - Server 2012R2 - running DHCP, DNS, AD

TFTP service: IP to be confirmed, VM on Wintel box, service on freePBX or other. (I need this as the handsets are Cisco 7940s)

Free PBX: with DNS pointed to and default gateway to:, DNS to

IP handsets: 192.168.1.x via DHCP, DNS, DG (This is the bit that I’m second guessing), freePBX settings etc all to


The new router [likely] can’t be on the same network as your AT&T box; I’d say this is asking for trouble. We have our voice traffic go onto a VLAN and then on our SonicWALL, it routes the traffic on that VLAN out a second WAN connection (EoC) instead of our crappy U-Verse box. I’d suggest getting an edge device (others have said SonicWALL is bad news, for us it’s fine) and setting up routing on that. You could even just set the routes based on IP range instead of using a VLAN, but that would be a bit tougher, assuming your switches support VLAN.