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We have an IP phone system in our office, and about 8 VoIP phones running on the system. We have a remote worker, who is literally states away.

We'd like to connect his phone to our VoIP network, so that he has a business phone and an extension to which we could transfer calls.

I was thinking, although I don't know for sure, that a pair of Cisco routers could be used in some way to make this work. I imagine a VPN solution, where I have one router connected to the phone network and the other router connected to the remote phone. Then have a site-to-site VPN set up so that the remote router...

And that's where I'm stuck. I know the remote router will need to use the DHCP server of the phone system. I've never set up something like this, so I am seeking the help of the community here.

What is the best way to get this remote VoIP phone RELIABLY connected to our internal VoIP network?

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2 Answers 2

Any router pair will do - they don't have to be Cisco - and, yes, a VPN is the way to go. Certainly stick to a pair of routers that support a hardware VPN and, if possible, assign a static IP to the phone; DHCP will work but it's nice to know the exact IP of the phone for quick troubleshooting

The setup should work - the only thing that tends to kill remote VoIP is if the link suffers from high latency but I have run remote VoIP phones across VPNs on ADSL with no problems whatsoever. What phone make and model are you using at the remote end - it would be useful to know in case there are any specific quirks with the make/model.

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It is a Nortel IP1230 I believe, I am waiting for verification. He got the phone before I started working here, and nobody ever set it up... –  Mistiry Jul 11 '11 at 21:04
    
We use ADSL so that is good to know! –  Mistiry Jul 11 '11 at 21:05
    
Ha - Nortel's one of few brands I have NOT used so I'll shut up now! –  Linker3000 Jul 11 '11 at 21:54

Yes, provided the VPN itself is reliable - ie low latency and virtually no packet loss this is definately possible.

It is not possible to know the ins and outs without detailed information about your configuration, but in general provided the PABX and phone can see each other without any NAT, and any configuration for the phone is manually specified or handed out via DHCP (or the phone is configured to look to the IP address of the PABX for deploying its configuration) it should just work.

Of-course you need to ensure there are no firewalling issues. In many cases once you "VPN in" you are part of the network and there are no firewalling restrictions, but this might not (and in a professionally run, high security network should not) be the case - in which case the firewall will need to be adjusted.

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