I have a VOIP server behind my firewall.
Currently, I am having trouble getting it to talk to various VOIP service providers. The cheap ones only use SIP which uses allot of ports and has NAT issues. Attempts with IAX have worked well, but those providers cost more.
I have to open so many ports to make the various SIP and IAX connections that I am hesitant to do that with my corporate firewall and add other risks to the company. Also, my firewall uses NAT.
I am also concerned that if I harden this server with too much host based firewalling/filtering (to be able to put it outside the firewall) that it may affect performance of the VOIP.
So I am trying to figure out how to put a router/firewall in between my ISP's router and my VOIP server.
I am thinking like this: ISP Router (4.3.2.1)-------(4.3.2.2)My Router(4.3.2.1)-------(4.3.2.2)VOIP Server
I hope that makes sense. I want to use a Real IP Address on my VOIP Server without having to have any changes made on my ISP's Router.
Is there any kind of transparent routing feature like this available in IOS? If there is, I can do most of my filtering in that router and just minor filtering on my VOIP Server.