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We have two offices (China and US) connected by site-to-site VPN using 2 Linksys RV082's. We also have a VoIP system with 2 VoIP phones in the China office. We have been having trouble with the phone connections, and our VoIP provider is asking me to have the China phones route over the VPN before going out to the internet.

US LAN = 192.168.188.x

CHINA LAN = 192.168.166.x

I can manually set the IP on the phones in China. How would I force the phones there to go out to the internet across the VPN first? If they have a 192.168.166.x IP, they will go to the China router and then out to the Internet. Is it possible to force them to go to the US router instead of the China router?

Any ideas would be greatly appreciated.

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Routing VoIP phones across the world is not going to solve your call quality issues, it might even make them worse. You'll lose any QoS effect that the circuit you are currently using provides. If that is what your provider is telling you, it is time to get a new provider. – MaQleod May 13 '11 at 20:00
up vote 2 down vote accepted

The VPN concentrator is on the same subnet? Change the default gateway on the phones. You may have to meddle with MTUs, though.

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The VPN routers are on each subnet ( and Our first inclination was to just change the default gateway on the phones to point to the US router. But won't the phones have a problem if the IP and gateway are on different subnets? – charnley May 13 '11 at 16:04
No, the gateway has to be on the phone's subnet. The VPN router on the China side should be able to route it once the packet gets to it. – Hyppy May 13 '11 at 16:16
So the idea would be to force the phones to go to the internet over the VPN, which would be a setting on the China router? – charnley May 13 '11 at 16:24
Static route on router, default gateway on the phones, separate VLAN/subnet off the VPN router, whichever you want to use. It can be done in many ways. – Hyppy May 13 '11 at 16:26
Okay thanks I am investigating VLAN/subnet option now. – charnley May 13 '11 at 17:20

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