General Guidelines for Routers Adjustments

This guide is intended to help you with routers that are not listed as recommended by Telebroad.

You may own a router that is not listed in our buying guide as recommended or adjustable to work with Telebroad’s telephony solutions. While we can only guarantee optimal performance with the routers we mentioned, you may still want to try and use your existing equipment first.  You can try the following general adjustments guidelines to implement to facilitate compatibility with Telebroad’s telephony solutions. 

You are advised to seek additional specific information for your situation in regard to each guideline and handle any adjustments after consulting your Internet Service Provider, network administrator,  and a network security expert where applicable. 

Automatic VoIP features

Routers will sometimes come with features designed for VoIP performance or sometimes sense existing network and apply suitable customization via a wizard or in the installation process. But such VoIP specific customizations usually achieves the opposite, resulting in interference to optimal VoIP data flow . The Telebroad system does not require any specific VoIP features. You should turn off any such feature you can see or decline installing or activating it from software wizards.


This is an extension of the above advice. SIP stands for Session Initiation Protocol. It is a communications protocol for controlling multimedia communication, specifically in our case VoIP traffic. ALG stands for Application Level Gateway. It is a  a security component found in many commercial routers that augments firewall security and is aimed at preventing some of the problems caused by them. It is also sometimes referred to as SIP Inspection. 


When it comes to VoIP the ALG may modify VoIP data to allow it to pass through the firewall,resulting in reduced quality and performance or even even complete loss of audio signal or connection. You should therefore turn off this feature. 


SPI and DoS Protection

SPI stands for Stateful Packet Inspection. It is another firewall security feature often included in a business networks. It only allows data matching known active connection to pass through. DoS stands for Denial or Service and is a kind of network attack aimed at overwhelming a computer network and making it dysfunctional. Both protections help the router to identify and approve or reject data for security reasons. 

However, because of the nature of telephony data these protections usually misdiagnose valid VoIP traffic as a security risk and therefore should be turned off. The problem is more likely to appear on a larger scale operation where many phones are involved leading to a blockage of traffic. Before turning off DoS protection see if there is an option to increase the number of connections acceptable by it. This will basically raise the threshold for the amount of traffic it will allow to pass before triggering a block. 


Double-NATing Conflicts

NAT stands for Network Address Translation. It is an essential network technology that allows multiple devices to share a single IP address.

Double NATing is a situation where more than one router is performing the address network translation on a network. The most common example is a Wi-Fi router that is connected to a Cable or DSL modem where both devices have NAT enabled (generally Cable modems presents less problems in this regard). Double-NATing is known to cause problems for VoIP phones.

To solve the problem you can try to put the modem in “bridge” mode by accessing its settings with a web browser. This will  essentially disable NATing for the specific device and make your network receive the public IP address and perform the NAT function only from the other device (the router). 

If this doesn’t work can try putting the second router IP Address in your first router’s DMZ - Demilitarized Zone. The DMZ allows all traffic to pass through without any translation and hence in theory will counteract the effect of double NATing.  Since sending traffic through the DMZ can expose you to security risks, this configuration should be consulted with a network security expert to make sure it does not introduce vulnerabilities into your network. 


IP Telephony Protocols

UDP - User Datagram Protocol, SIP - Session Initiation Protocol, and RTP -  Real-time Transport Protocol are all technologies that needed for the proper functioning of IP Telephony. Make sure you are not blocking any of them. Restrictions on any of these protocols in your firewall settings may cause one way or no audio during calls or completely block calls. Outbound restrictions are particularly crucial in this regard. Any modifications to your firewalls should, again, be handled with the advice of a network security expert.

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