Question : Multi-phone VoIP  Issue

Here's the issue, as strange of a setup as it might sound. We have a remote home-based user who has an existing VoIP phone utilizing a Cisco ATA186 device. Not sure of the provider just yet. We recently installed a Mitel TeleWorker solution in her house as well. The problem is, both phones work sporatically when they are both online on her home network. Meaning that if you try to ring her on the Mitel phone, neither party can hear. As soon as she disconnects her Cisco device, the Mitel works beautifully.

Can two different VoIP solutions not reside on the same network? Is there a way around this to fix?? Any help would be greatly appreciated as we need to resolve this ASAP!

Thanks,
Phil

Answer : Multi-phone VoIP  Issue

Well, you have 4 options:
1. Get another internet connection for that VoIP phone.
2. Create a VPN tunnel between her site and yours and give her phone a static IP so that you can route across the VPN tunnel.
3. Forward one phone number to the other.
4. Get a different piece of equipment like a Cisco 2621 or something with two ethernet interfaces, get two IP's from an ISP, put static internal IP's on the phones and do a static NAT on the router to each phone.

The problem is according to the RFC for RTP, the source port is not the same as the return source port. It is designed odd/even. If I place the call, the source port could be 5000 but their return port is going to be 5001. It doesn't work unless you use static nat so you can't do port translations on the router for port 5000 to be 4000 because the return port is going to be 4001 which may conflict again with the other phone. This is why only a static nat will work.

Sorry to be the bearer of bad news.