I can't make calls

What is worse than a dropped call? The inability to make the call in the first place.

While rare, sometimes businesses are likely to experience the dreaded “X” on their IP phones where they are outright locked out of the ability to make calls over their devices.

Why It Happens

The main culprit in this case tends to be a well-meaning feature called SIP ALG whose main use is to help push outbound VoIP packets through existing firewalls without having to adjust them, but can sometimes lead to the packets getting routed to the wrong IP address, which results in the inability to connect to the desired party.

It can also happen when using two routers that can create unnecessary network load.

How To Fix It

The easiest way to fix this issue is to disable the SIP ALG option and configuring the firewall properly as well as avoiding the use of more than one router where possible, or placing the businesses VoIP phone network on a VLAN if the former is not possible.

You’ve highlighted an important VoIP issue – the inability to make calls due to the interference of SIP ALG (Session Initiation Protocol Application Layer Gateway) and potential complications with multiple routers. Let’s delve further into the causes and solutions for this problem:

Causes:

1. SIP ALG Interference:
   • SIP ALG is intended to facilitate the traversal of VoIP traffic through firewalls, but it can sometimes misroute packets, leading to the inability to connect to the desired party.
2. Two Routers and Network Load:
   • Using two routers in a network can create unnecessary complexity and network load, potentially affecting the ability to make VoIP calls.

Solutions:

1. Disable SIP ALG:
   • The primary solution is to disable SIP ALG on routers or network devices. SIP ALG can be well-intentioned but may cause more harm than good in certain scenarios.
2. Configure Firewall Properly:
   • Ensure that the firewall is properly configured to allow VoIP traffic. Adjust settings to accommodate the specific requirements of the VoIP system being used.
3. Avoid Multiple Routers:
   • Whenever possible, avoid using multiple routers in the network. Simplify the network architecture to reduce potential points of failure and streamline VoIP traffic.
4. VLAN (Virtual LAN):
   • If using multiple routers is unavoidable, consider placing the VoIP phone network on a dedicated VLAN. This helps segregate and prioritize VoIP traffic, reducing the risk of interference from other network elements.
5. Update Router Firmware:
   • Keep router firmware up-to-date. Manufacturers may release updates that address known issues, enhance compatibility, and improve overall performance.
6. Testing and Monitoring:
   • Regularly test the VoIP system after making configuration changes and monitor for any issues. This proactive approach can help identify and resolve potential problems before they impact the ability to make calls.

By implementing these solutions, businesses can mitigate the risk of being locked out of the ability to make VoIP calls and ensure a more reliable and consistent communication experience.