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VoIP through VPN

I keep hearing I will run into problems trying to do VoIP through a VPN. I want to have an 8 port 3002 with a PC in one port and the IP phone in another. The users will be connecting through a fractional T1 (128Kbps) from the same ISP as the central office with only one hop between the 2 sites and well under 200ms latency. Has anyone done this ( or something similar) successfully? My ultimate goal is to replace the analog phone lines at the remote sites completely.

Community Member

Re: VoIP through VPN

Yes, it can be done and works quite well. What kind of equipment are you using on BOTH sides? I ran into problems with a 2621 and encryption card being able to handle more than 3 or 4 calls while doing encryption. It killed the CPU. It could handle TCP traffic all day long, but the UDP/RTP traffic really gave it a workout.

Re: VoIP through VPN

Thanks for the reply. On the remote sites I will be using an 8 port 3002 with the PC in one port and the 76xx IP Phone in another. They will be doing VPN into a 3005 VPN Concentator and the Voice Gateway is a VG200. I will be running Call Manager as well. There should only ever be 5 or 6 calls max at the same time. Your thoughts?

Community Member

Re: VoIP through VPN

I don't have any experience with the 3002 or 3005, so I can't say. 128K should be adequate bandwidth for one phone, you may want to adjust your MTU to reduce the serialization delay. What's the bandwidth coming back into the main site? My 2621 with a hardware encryption card should be able to handle 5 g.729 phone calls, but it can't. Unencrypted, it works great. I'm probably going to open a case on this, because it seems like it should work without a problem. Good luck.

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