Saturday, 7 May 2016
Don't Buy The Cisco SPA122 VoIP ATA
At first glance, one might get the impression that this is an anti Cisco headline. Quite the opposite - I've been a fan of Cisco ATA's for quite a long time. After all, they have been the work horse ATA's in the VoIP industry for many years.
Many VoIP service providers that resell VoIP ATA's will most often offer the Cisco line of ATA's as their first choice, if not the only choice of ATA for their customers.
All that said, it is my opinion that most (or I should say - far too many) DIY and VoIP service provider customers end up being sold the SPA122 when all they need is the Cisco SPA112.
In the past, I have received a significant number of emails requesting support/advice about problems people are having with their Cisco SPA122 ATA's. In the end, much of their VoIP problems are related to the fact that they are double-NATing - which is frequently an issue for VoIP.
What do I mean by "double-NATing"? As the term implies, your VoIP phone is essentially operating behind 2 NAT router firewalls - which for VoIP is often problematic.
In general, VoIP devices have enough challenges operating behind a single NAT router firewall. NAT router traversal faces issues such as SIP and RTP port blocking (i.e., Session Initiation Protocol and Real Time Protocol ports blocked). To overcome these obstacles, ATA configuration tricks like enabling "NAT Mapping" and "Port Keep Alive" must be incorporated. Sometimes, it becomes necessary to enable STUN Server support to help the ATA discover and report its public IP address to the VoIP proxy server.
Challenges arise when operating a VoIP ATA like the SPA122 behind another router such as the Modem/NAT-Router supplied by your ISP or your already personally installed NAT-Router behind your ISP Modem. In this case, you are... "double NATing".
In this situation, it is almost always "advisable" to reconfigure the SPA122 to operate in "Bridge Mode" vs. the default "NAT Router Mode".
In the end, it is my opinion that the vast majority of BYOD - DIY and customers of low-cost VoIP services should not by purchasing a Cisco SPA122. Instead, they should be purchasing and using the Cisco SPA112.
Not only is the SPA112 more appropriate for most users, they inevitably have less issues caused by double-NATing, And, they don't have to wast time and energy contacting their technical support, or me, and trying to figure out how to configure their SPA122 for Bridge Mode - which in the end, functions exactly the same as the Cisco SPA112 ATA.
The SPA122 functions exactly the same as the SPA112 when the SPA122 is in bridge mode. In fact, both ATA;s run on the exact same versions of firmware. Only difference is that the SPA122 has has a built-in NAT-Router while the SPA112 does not.
99% of people (if not 99.999%) are already behind NAT Routers (and should be). So, why buy an SPA122 ATA? Don't.
Do yourself a favour if you are in the market for a new Cisco ATA. Don't buy the SPA122. Buy the SPA112 instead.