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New Member

IP telephony across a VPN


Can you connect an IP phone to a CCME if they are not on the same subnet? For example across an IPsec/GRE vpn.

Thank you,



Re: IP telephony across a VPN

If a call needs to connect to a CCME at a different location it must be built and the TFTP server must be from that location.

For instance our HQ office, we also needed to open the IP for the phone in the firewall to allow traffic to flow, calls to process.

What will happen is the IP address from that location will be given to that device so it will be on the same subnet at that point.

Hall of Fame Super Gold

Re: IP telephony across a VPN

Yes, there is no problem in doing that. Only, you want to properly setup your routing so that any subnet where are phones, can communicate with all the others. If you cannot do that, configure "mtp" under the remote ephone.

Hope this helps, please rate post if it does!

New Member

Re: IP telephony across a VPN

There are some special requiremens for this to work on a public internet VPN.

I heard that the round trip time must be under certain value.

Thak you again,


Hall of Fame Super Gold

Re: IP telephony across a VPN

Hi, I have sites with RTT of like 900 ms (vsat) and they work just fine.

Thanks for the appreciation and good luck!

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