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How to configure VoIP through firewall


We have a VoIP solution that is currently directly connection from the ISP router into our network. I need guidance on how to configure VoIP to traverse a firewall.

We have a secure redundant solution for the data connection, but I have no idea when it comes to VoIP as to which ports and protocols to allow/ block with achieving optimum security.

  • This is a Hosted Voice Solution with Call Manager at the ISP.
  • There is a PA-2FE-TX card that provides the VoIP from the router.
  • The router provides DHCP for the Phones only.
  • There is an internal windows DHCP for the PCs.
  • Data and VoIP provided by same ISP.

Attached are diagrams of a) current set-up and b) what I’m aiming for.

Any help is appreciated. Thank you.


Re: How to configure VoIP through firewall

Your phones use SCCP or SIP protocol to communicate with CM + TFTP for config and firmware, you need to open RTP stream to phones - not sure where is your voice GW. Probably you will need HTTP/HTTPS or someting more like LDAP or Cisco Directory.

More less that's all but best option is to check with ISP what need to be open exactly.

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Re: How to configure VoIP through firewall

Take a look at this:

There is a TCP and UDP port usage document under each version of Call Manager. They are a pretty good guide as to what you may need to open in your firewall.



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