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By WelshPaul
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The Cisco SPA112 VoIP ATA (Analog Telephone Adapter) is the next generation SIP based (Session Initiation Protocol) ATA that replaces the Linksys PAP2T.

In this article, I shall walk you through the basics of how to quickly (relatively speaking) configure your shiny new SPA112 ATA for use with almost any SIP-based VSP (VoIP Service Provider) that offers BYOD connectivity.

To achieve this goal, I will be using the ATA as configured with it's factory default values. Then, I will point out only the essential settings (typically) that "must be edited" in order to connect and achieve service registration with your favourite BYOD VSP.

In order to proceed with the quick and easy setup procedure, a few assumptions must be made and prerequisites met.

Assumptions and Prerequisites
  • You know how to login to the SPA112 (See here.)
  • The SPA112 has not been locked-down by a VSP or previous owner.
  • Make sure the ATA is Ethernet connected to a LAN port on your NAT Router.
  • The NAT Router must be set to issue DHCP IP addresses to LAN connected devices.
  • You have Port Forwarded or Port Triggered SIP ports 5060 - 5061 in your Router.
  • You have Port Forwarded or Port Triggered RTP port range 16384 - 16438 in your Router.
  • By default, your NAT Router will provide DNS lookup with the default DNS servers defined by your ISP supplied Internet Modem. And, by default, your SPA112 will use the DNS lookup servers as referred by your NATRouter. This may be just fine, in general. However, some people, including me, like to specify highly trusted and known secure DNS servers for their local networked devices. If you set your NAT Router to use specifically trusted and security conscious DNS servers, then all the DHCP enabled devices on your network will also use those same DNS servers for Internet name lookup (including the SPA112). Here are some widely suggested DNS servers you can set in your NAT Router and/or PC's and ATA's:

    - Open DNS: and
    - Google Public DNS: and
    - Norton DNS ConnectSafe Policy 1: and
  • You have an analog telephone plugged into the ATA Phone 1 port.
  • You know how to perform a Factory Reset (Reset Configuration to Defaults) - see here.
  • Once you know how to perform a Factory Reset, I recommend that you do so before proceeding.
  • Your SPA112 is running the latest Cisco Firmware version. If not, see here.
  • Your SPA112 is powered-up and ready to be configured.
  • You have consulted your VSP support pages for their specifically specified service settings and values. Most settings I describe below depend on knowing the "specifics" of your VSP required settings.
Now that we have all the assumptions and prerequisites out of the way, what remains is only the non-default essentials required to successfully configure and register the SPA112 with your VoIP provider.
So, lets get started.
  1. Login to the SPA112 Configuration Utility using your PC web browser.
  2. Forget about using the Quick Setup page on the SPA112. (I explained why here.)
  3. Navigate to (click on) the Voice menu option.
  4. Click on "Line 1" menu option (left-side of navigation window pane).
We have now landed on the page where all the action is.
SPa112_Voice_Line1.jpg (77.3 KiB) Viewed 13052 times
At this point, all values you see should be their Default values. This way we will know we are on the "same page" (figuratively speaking) when it comes to having the same configuration settings as a starting point (no surprises).

While there is a mind boggling array of configuration parameters listed here, we only need to configure about a dozen or less of these parameters to get the ATA ready to make successful SIP protocol based VoIP phone calls.

VoIP Service - Network Configuration Essentials:
Every SIP based BYOD VSP requires that you connect to the proper VoIP server (proxy). In the SPA112, you need to edit the Proxy field:
  • Proxy
  • This will typically be the VoIP service domain or sub-domain name URL.
    Something like:, or, etc. However, in some cases you may be able to input the specific server IP address. (not generally recommended)
Optional Network NAT Traversal Settings
Often, you may need to enable the following NAT traversal settings:
  • NAT Mapping Enable
  • NAT Keep Alive Enable
Check with your VSP's support pages for their recommendation on NAT traversal settings.

If your VSP doesn't specify NAT mapping and keep alive settings, then my general rule of thumb for these settings are:
  • If you are missing incoming calls on your ATA (perhaps, only intermittently), it's probably because of NAT traversal issues. In which case, try setting NAT Mapping and NAT Keep Alive Enable to YES.
    This assumes the ATA is behind a NAT Router (most people do use NAT Routers)
Some VSP's will require additional VoIP network server settings:
  • Outbound Proxy Some VSP's may have a cluster of proxy servers for load-balancing purposes. The outbound proxy will forward server requests to the appropriate server within the cluster. Often, the outbound proxy domain name URL will be the same as the main domain URL. Your VSP will have the appropriate information listed on their web site support pages (or, in an email sent to you).
  • Use Outbound Proxy
    If you enter the name of an outbound proxy, then you also need to enable the setting called Use Outbound Proxy by setting its option setting to: YES
  • Register Expires
    The default usually works (3600), however, I'm now seeing some VSP's recommending you set shorter registration periods. e.g. 360, or 120, or as low as 60. (Values are in seconds.)
  • Use DNS SRV
    Some VSP's will require you to use the DNS SRV option in your ATA.
    In which case, set the option to YES. The default value here is typically set to No.
  • DNS SRV Auto Prefix
    If your VSP requires DNS SRV to be enabled as above, then they will likely also suggest that you to set DNS SRV Auto Prefix to YES.
The configuration settings illustrated below, circled in Red, are either required, or optionally required, depending on your VSP's specifics. (May need changing from the default values)
SPA112_Voice_Line1_2.jpg (85.86 KiB) Viewed 13051 times
VoIP Service - Subscriber (User) Configuration Essentials:
Once you have entered the VoIP servers and their related configuration settings, the ATA will have to login and be authenticated with those servers.

Every SIP based BYOD VoIP service will require, at a minimum, the following User Login credentials:
  • User ID
  • Password (also known as your SIP password)
Depending on your specific VSP, you may be required to enter the following additional login credentials:
  • Auth ID
    Enter the Auth ID value as specified by your VSP.
  • Use Auth ID
    If you enter a value into the Auth ID field, then you must also Enable it by setting Use Auth ID to YES. The default on this is No.
VSP Specific Dial Plan
The dial plan configuration values as set by the SPA112 defaults will enable you to make traditional types of phone calls. However, you should consult your VSP support pages for their recommended dial plan settings for dialling special vertical service codes, voicemail, etc.

Start Making and Receiving SIP Based VoIP Phone Calls
That's it. I have now covered the bare-bones essentials of getting started configuring your SPA112 ATA with a BYOD VoIP service provider.

If you started with the SPA112 configuration default values, and only changed the values and entries described in the above bullet points as specified by your VSP, you should have a dial tone and now be able to make SIP calls with your ATA using your favourite VoIP service provider.

Obviously, there are numerous additional settings for tweaking the configuration and performance of your ATA. But, the bare bones basics was the theme of this article.

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