Cisco 79xx

Note: While Cisco 79xx phones may work with OnSIP, we recommend reselling your Cisco phones on eBay and using the funds for new Polycoms. The benefits of using Polycoms over Cisco 79xx include:

  • Music on Hold
  • High Definition (HD) audio
  • Boot server and asset tracking via OnSIP WWW site
  • Automated configuration
  • Automated software upgrades
  • No local tftp server necessary

Known Issues

Cisco has stated that they will not continue to develop SIP software for the Cisco line of phones, so our recommendation is not to invest in a Cisco phone for use with OnSIP. We are providing these instructions as a courtesy for customers who have already purchased these phones. This is the limit to which we can assist with the configuration and use of the phones, and if changes in our infrastructure break features or usability, we will not resolve them.


Read this.

  • Phone network configuration completed.

    The following instructions assume your phone has successfully booted and completed network configuration including obtaining valid IP addresses for itself, an IP gateway and DNS servers either via DHCP, manual or other means, that your phone is running with factory defaults and that the SIP image has been loaded. You will also need to have a running TFTP server.

  • Phone is running firmware release 8.3.2 SR1.

    You can find the firmware version your phone is currently running by using the "Settings" button on your phone and navigating to Status -> Firmware Versions. If you are running a version prior to 8.2, please upgrade your phone's software before proceeding. We have had the most luck with 8.3.2 SR1. 

  • No Audio on Inbound Calls
    The magic setting is nat_address.


    The WAN IP address of the Network Address Translation (NAT) or firewall server. You can use either a dotted IP address or a DNS name (A record only).

    Apparently, Cisco 79xx phones DO NOT handle NAT properly without this setting. (There are forum posts after forum posts going back 8+ years about these stubborn little bastards.) If you change nat_address so it has the external IP address of the connected network and then reboot the phone, it will show up registered without NAT and then function perfectly. The phone still has a private IP address but is manipulating something in the packets/headers so it doesn't appear to be using NAT.

Phone Configuration

Step 1. Gather information for each user.

Each user has a set of credentials which will be needed to configure each phone. For each phone that you are configuring, obtain the following:

  • "SIP Address" (Address of Record)
  • "SIP Password"
  • "Auth Username"
  • "Username"
  • "Domain"
  • "Outbound Proxy"

You can find this information in the user detail pages under the Users tab in the "Phone Configuration" section.

Phone configuration section


Step 2. Create the configuration files for the phone.

The Cisco 7960 phone is configured via two .cnf files that the phone will need to download from your TFTP server. This is the only method of configuring the phone.

The first of these files is SIPDefault.cnf, which sets the default parameters for your organization. This configuration worked in our lab:

Configuration file for phone

Dynamic Settings - as of July 2018 per customer report
proxy1_address: Proxy/Domain
proxy_emergency: Proxy/Domain
proxy_backup: Proxy/Domain

image_version: P0S3-08-11-00 (needs to match what's on the phone)
nat_enable: 1 
proxy_register: 1 
timer_register_expires: 600


The second of these files is SIPMACAddress.cnf, where the MAC Address is the specific MAC address of your phone. This is where the individual line configuration is stored for the user of the phone. This configuration worked in our lab:

Configuration file for phone

Dynamic Settings - as of July 2018 per customer report
line1_shortname: Proper name or extension name
line1_displayname: Company Name or another descriptive name
line1_name: Username
line1_authname: Auth Username
line1_password: SIP Password
proxy1_address: Domain 
proxy1_port: 5060 
proxy_backup: Domain 
proxy_emergency: Domain 
phone_label: Company Name or Extension Name


Step 3. Load the Phone with the Configuration Files

Save SIPDefault.cnf and SIPMACAddress.cnf to your TFTP server.

Configure the phone to point to your TFTP server by going to "Settings" -> "Network Configuration" -> "TFTP Server". Type in the IP Address.

Reboot the phone.


Step 4. Confirm that your phone is registered.

In the Admin Portal, click on the "Users" tab. You will see a green "online" notation next to each user with a registered phone.


If you are experiencing trouble, double-check your settings as described above and be sure to verify that your password was entered correctly without any leading or trailing spaces.


Additional configuration tips added July 2018 per OnSIP customer using one of these phones.


See our top business VoIP phone recommendations 

Download the 2017 Business Phone Guide

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