VoIP over VPN



  • Hello everyone :)  I am seeking help.

    I have two networks connected over the internet via a pfSense to pfSense OpenVPN tunnel.  Both pfSense boxes are of the ALIX 2D3 variety.

    On one network there is an Asterisk server and a Cisco 7905G phone (using SIP connected to the Asterisk server), amongst other stuff.  On the second network there is a Cisco 7960G (using SIP) connected to the remote Asterisk server through the VPN tunnel.  I have attached a network layout for your viewing pleasure!

    Both pfSense boxes were up until recently different IPCOP devices, and with a VPN tunnel between the two the setup worked perfectly.

    Since the change over to pfSense and the ALIX boxes a strange thing happens, on calls between the two Cisco phones the 7905G (on the same local network as the Asterisk server) has short periods (1 seconds or less usually, though on one occasion was upto 10 seconds) where they cannot hear the caller on the 7960G.  During the conversation this happens quite frequently e.g. once every few minutes.  The odd thing is the 7960G user does not experience any loss.

    The tunnel is an OpenVPN AES-128-CBC Shared Key tunnel.  I started out with a UDP, and then tried TCP, and I have since added 'engine cryptodev' to the custom configs on both.

    At the times of the calls there is usually no other internal or external traffic on either network, and as mentioned before this is a problem that has been introduced since the changeover to pfSense, so I am hoping I have missed something out form the VPN setup which would help things.

    Any thoughts or suggestions as how I might improve this will be very welcome.

    Thanks in advance,

    Bill
    ![network layout.png](/public/imported_attachments/1/network layout.png)
    ![network layout.png_thumb](/public/imported_attachments/1/network layout.png_thumb)


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