One of the common problems with with VoIP phone service is your particular phone or phones may receive strange calls at strange hours with caller ID numbers that are not full 7 or 10 digits, in fact they me be just a single digit. This almost exclusively ties back to a Router issue(s):
1) The router is a store bought, low end router. Many sub $100 routers provide basic connectivity to the internet for web browsing and common applications with a few home users, but when tasked with voice and video applications they quickly run into problems due to design and component issues. Running a small or medium office with one fo these will typically lead to several problems including dropped calls, one way audio, and other assorted issues. If you have a customer coming aboard or experiencing ongoing problems it is best to address this problem as soon as possible. We can reccomend quality routers if requested.
2) The Router has a feature called "SIP ALG" turned on. This feature was designed to help VOIP phone applications, but they did not have service providers in mind. What this feature is famous for is causing one way audio. The reason for this is that is replaces the private NAT ip address of the phone with the Public router ip address. This feature should always be turned off since our service addresses NAT issues correctly!! When combined with a SIP listening port issue, the problem multiplies with strange calls from scammers/hackers and one way audio.
3) The SIP Listening port of phone is default to the worldwide standard of "5060". With a good functioning router handling "NAT" correctly you will not have any issues. But if your router is having problems or combined with "SIP ALG" issues, your phone will respond to someone on the Internet running a rouge application to find voip services they can exploit. In most cases they will not be able to exploit, but you will receive strange calls typically at late hours with strange caller IDs. If you cannot fix the router, you can change this SIP Listen port on most phones to anything other than "5060". We have a seperate article on changing the SIP Listen port, make sure you don't change the SIP Server port from "5060" which is different and required to register your phone to the service.
The bottom line is you need the following for good, reliable service and we will provide the rest:
- Quality internet connection with enough bandwidth in BOTH DIRECTIONS. Each call requires about 90kbps in BOTH DIRECTIONS at the same time. Remember this has to be above all the other internet traffic that it shares like web browsing, social media, file downloads, etc..
- Quality router. It does not have to be the most expensive router, just try to avoid small, sub $100.00 store bought routers when possible.
- Quality ethernet switch connecting all the SIP Phones and Computers together. Though this is less likely to cause you problems, the cost of a good 100mbps or 1000Mbps switch has come down dramatically over the years. The Sub $100 ethernet switches in the stores will typically work for small applications or single users, but its not a good idea for small to medium office environments. Many offices start small and get a cheap router and switch to start, then grow by adding more of the same.
- Make sure voice is the priorty traffic when going out of you router to the Internet. Most routers have an option for this. 3rd party bandwidth optimizers are the best when you have larger offices with many PCs/laptops/tablets using the same bandwidth.
- Turn SIP ALG off. Most Routers have an option to turn this on or off. By default they usually have this turned on.
- Change your SIP listen port from "5060" to anything else on your SIP Phone.