I would like to ask a question I have about the usage of LAN Telephony – DMZ Issue. We have a service based on IP Phones and analaog adaptor. Many of the users are behind a router on a LAN. The outgoing services work fine but when it comes to incoming calls on the IP (On-Net) calls, If the device is on DMZ it works and if not, it does not. We currently use H323 standard. Someone advice me to migrate to SIP as they told me that user wont need to DMZ in order to receive the calls from other IP Phone users. We are not ready to migrate to SIUP at this moment. Also we have a lot of users who travel and stay at hotels and they do have LAN connections there but no DMZ facility. Please advise if someone has experience on this and how to overcome. What options are available?
If you control the receiving end of the calls,like calls from hotels to your gateway or call relay, there is a very easy,simple and not too expensive solution: VPN router.
Get a cheap VPN router, put the VPN router on the customer premise, betwen the I.P. phone and the LAN/internet.
On your gateway, put another VPN router on front of the gateway.
The customer will “tunnel”trought the NAT and even some firewalls, for sure they will go trought the hotels NAT.
The drawback: Use of bandwith will be higher, because the VPN encapsulation and encription .
If yu could find a router that does tunneling without using any encription, that will be perfect, but so far I have not found any.