How is your system set up?

If your business is set up with a top-quality VoIP phone system, but recently you have been experiencing too many dropped calls, or maybe your phone keeps ringing even after you answer it. Perhaps you haven’t been getting your incoming calls at all?

No worries. Feel calm and confident to know that you will be able to resolve your voice-over-internet issues quickly. It can be as mundane as a simple disable of what pros call SIP ALG. SIP ALG can and sometimes should be turned off. Keep reading, and we will discuss what exactly SIP ALG is and should you disable it? Also, some valuable bonus data on fully optimizing your network for VoIP phone service. 

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What is the WWW in SIP ALG?

SIP ALG is an abbreviation for Application Layer Gateway and is present in almost all commercial routers and has this feature turned on by default. The primary purpose is the prevention of issues caused by firewalls. 

It consists of two different technologies:

  • Session Initiation Protocol (SIP) is the underlying service that powers all Voice over Internet Protocol (VoIP) phones, apps, and devices. The SIP manages registering devices, maintaining call presence, and overseeing the call audio.
  • Application Layer Gateway (ALG) – Routers segment your internal network through a process known as Network Address Translation (NAT). Then, the ALG becomes a proxy to rewrite the destination addresses in data packets.

The main issue with SIP ALG is the packet rewriting aspect of it. SIP ALG can help mitigate multiple NATs, but it doesn’t help in overall performance. 

Issues with SIP ALG and VoIP Systems

A user might experience various symptoms with SIP ALG activated on a VoIP phone. Sometimes these are hard to initially discover, especially since these issues often happen quietly without users being aware. Problems like one-way audio, where only one person is clearly hearing and communicating, while the other end is silent. Phones not ringing properly when called, or having calls prematurely end when you are talking. Sometimes, users might discover that all their calls go directly to voicemail with no apparent cause

Related: What is VoIP Numer Porting?

These types of interruptions happen due to a router’s firewall. Many routers today default SIP ALG to on within their device’s firmware. Thankfully with easy-to-manage web interfaces, simply checking or unchecking a box might fix some of the system problems.

A VoIP phone.

If you are having problems with your SIP ALG, it helps to have a pro on your side. Contact SE Telecom today

Should I Disable SIP ALG?

Yes! If you are a VoIP user with a virtual phone system in place, the best practice is to turn off SIP ALG entirely. The feature itself is usually enabled on most broadband routers because SIP ALG was first introduced with great intention to respond to the limitations of Network Address Translation

However, it has been found to interfere with the functionality of IP and signaling protocols. Working with today’s VoIP applications can cause more complications than help.

Unless otherwise instructed by your router manufacturer or VoIP provider, it is recommended to disable SIP ALG altogether. It would be best if you disable SIP ALG, especially when it:

  • It affects the reliability of phones and VoIP systems
  • Causes inbound faxes to fail
  • Refuses parked calls
  • Interrupts SIP traffic as with calls and conferencing apps
  • Isn’t required with cloud-based VoIP providers

Related: 20+ VoIP Features You Can’t Live Without

To understand a little more about how SIP ALG is problematic for modern SIP phone systems, you first need to understand the process that takes place when making a SIP call. 

First, the invite stage takes place, and this is when you reach out to another caller to initiate the conversation. Secondly, the invite response stage is when the connection happens. The answering stage is next and is the acknowledgment of an inbound call. Last, the confirmation stage occurs. This is the final step in call connection. Once these steps properly go through, the actual two-way call can occur.

The problem with this connection perspective is that having a step-by-step process like this means more of a chance of interruptions before ever even having the call. Each time the system confirms a connection attempt, the ALG then modifies the sent SIP packets. If any of these steps fail, the call will ultimately fail to connect. This is referred to as a failed registration and is most often caused by SIP ALG working in the background. 

How to Disable SIP ALG on Your Router

When in doubt, it is always best to speak to a network administrator or tech professional before changing any network settings. However, depending on your specific router model, disabling SIP ALG can be a simple thing to do. The method of disabling might just differ slightly depending on your brand of router. But if your SIP ALG is doing more harm than good to the performance of your VoIP application, here is a quick guide to disabling the feature on most routers:

Log into your router. This will need a sign-in and admin password to enter in most cases. Look under security settings, and uncheck SIP ALG. Make sure to save and reboot your router afterward. More advanced firewalls can tend not to be simple to adjust and may need port forwarding and more advanced navigations.

An employee working from home.

Best Advice for Reliable VoIP Performance

  • Utilize wired Ethernet connections whenever you can
  • Using gigabit switches and routers helps eliminate internal bottlenecking
  • Choose a high-bandwidth ISP with recommended hardware
  • Make UDP ( User Datagram Protocol) timeouts longer
  • Keep up on firmware updates
  • Set up a VLAN (virtual LAN) tagging for SIP devices
  • Select the right VoIP phone service
  • Disable SIP ALG settings
  • Consult with VoIP professionals 


Disabling SIP ALG can be the solution you are looking for when experiencing problems with VoIP calls. It is completely worth adjusting to enhance your virtual phone service’s reliability and overall performance. VoIP technology needs bandwidth, latency, and stability to function correctly. Disabling SIP ALG might improve inbound and outbound call quality and connection capability. 

For further help about implementing the best phone system for your business, contact SE Telecom today.