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I have Thomson TG587N Wireless-N ADSL2+ Router from o2 and I have a Siemens Gigaset C475 IP Phone connected to one of their Ethernet ports.

I have an account in and I used to login in to my voip account without any problems with the old router which was an non N thomson router (I don't have the specs on that one). No config changes were made on the phone and now it fails to login into my voip account.

I've turned the firewall off and still no connection. I can make voip calls from my pc and my iphone connected to the router by wifi.

Any guess?

Thanks in advance.

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Do you have the router set to DHCP/NAT? VoIP runs on certain ports and needs 100% full access to those ports. Even with the "firewall" off, you may need to forward those ports to the right device in order to have your VoIP service to work. You will need to get the ports that your service uses from your service provider.

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Thanks for your answer. But if I can make voip calls using an app on my pc and iphone connected with wifi, is there a chance that the ip phone wouldn't work because of NAT? shouldn't all equipments not work at all? – Txugo Nov 14 '10 at 0:50

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