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I have added a second VoIP device on my LAN, but it doesn't work.
Posted by Gabriel Yu on 11 April 2008 06:54 AM
This is probably because the VoIP Ports are Opened/Forwarded to the first device.  Check your router's NAT > Port Redirection and NAT > Open Ports configuration pages for entries containing TCP Port 5060.

There are several NAT Traversal options (including ALG, STUN, Outbound Proxy) which VoIP devices can use to communicate through a router - however these are not common in older routers (and older firmware for DrayTek routers).   Port Redirection works with all routers, but since a port can only be redirected to a single LAN device it means only one VoIP device can be used.

  1. Upgrade to latest firmware for your router, as this may add NAT Traversal options.
  2. Check whether your first VoIP device really requires the port redirection.  Maybe the port Redirection was a quick fix, and other methods will also work.
    • STUN requires an stun server address configured in the VoIP device, and the router must support stun.
    • Outbound proxy must be supported by both VoIP device and VoIP Provider
  3. Check whether your VoIP Provider can use other than port 5060.  If so you can redirect port 5061 (or whatever) to your second VoIP device.  Note that you may have to reconfigure VoIP devices and router so that each VoIP device uses a different range of UDP ports (for RTP packets). 
  4. If you are using VoIP for a business or organisation which may grow to several VoIP lines, you could consider connecting the VoIP device to your PBX; or implementing an IP PBX using Asterisk as the end-point for all the external VoIp connections. 
  5. Purchase a new router which does support VoIP.  May I suggest a Vigor 2700V or 2700VG  Vigor 2700 has 2 built-in FXS ports.  if you need to add more VoIP devices it supports STUN and SIP ALG, and has all the QoS options of the business-grade DrayTek routers.
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