How to configure VoIP through firewall

[Tom101]

Hi,

How do you configure VoIP through a firewall? The IP addresses are coming from a DHCP server that is located in the inside network, and i am trying to setup the telephony service on the outside router. Is this possible to do?

The main problem at the moment,is that the 2811 router is showing a 'Ambiguous command: "max ephones 1"' error when trying to add the ephones.

Another concern that i'm going to have is allowing the VoIP port through the firewall. 

I have attached a screenshot and a packet tracer file.

Any help would be greatly appreciated. Thank you. 

[Hudaifa shakkir Nattukallingal]

Hi,

Technically you can put the CME router outside the firewall if you want. (I don't understand the requirement for it, but its possible). You need to allow the required IPs and ports to allow in the firewall to communicate between the CME and the IP Phones. For the phones to reach inside DHCP server, you need to configure the DHCP relay for it.

For the error message for 'max ephones', I think the command is 'max-ephones'.  

Thanks.

Shakkir