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Understandings Of Sip 401 Unauthorized: Meaning & Solutions To Fix

Session Initiation Protocol (SIP) is popular for starting and ending real-time communication sessions in Voice over Internet Protocol (VoIP). 

The dreaded SIP 401 Unauthorized error is one of the customers’ most frequent problems. However, like any other network protocol, SIP does experience some difficulties. 

This post will explore SIP 401 Unauthorized complexities, looking at its significance, root causes, and potential solutions.

Table of contents:

Sip 401 Unauthorized Meaning

SIP 401 Unauthorized signifies that user authentication is necessary for the request. A SIP server may require user authentication when someone tries to access a protected resource there or starts a call. The server will return a “401 Unauthorized” status code in response to a client’s request that either doesn’t contain any acceptable credentials or gives invalid ones. 


Sip 401 Unauthorized error meaning


Simply said, the user is not recognized by the server as a genuine entity within the system, which results in the server refusing the request. The SIP server has returned this error message; the reason it is being sent to the softphone is unknown to anyone other than your PBX administrator or VoIP provider. 

Specifically, the error message informs the user or the device that it is not authorized or has insufficient credentials to create a SIP session. Essentially, the server says, “You must enter valid credentials to access this resource or carry out the requested action.”

Distinguish Between Sip 401 Unauthorized And HTTP 401 Unauthorized Error

SIP 401 Unauthorized error is a Session Initiation Protocol (SIP) error that only occurs when real-time communication sessions are initiated and terminated using VoIP systems. 

In VoIP systems, this error happens when a user or device lacks the authorization or credentials needed to create a real-time communication connection, prompting the server to refuse the request.

On the other hand, the HTTP status code 401 Unauthorized is a component of the Hypertext Transfer Protocol (HTTP), which is used for web-based communication. It signifies that a user cannot access the requested resource because their credentials are either insufficient or invalid.


Distinguish Between Sip 401 Unauthorized And HTTP 401 Unauthorized error

Although they are related to distinct settings and protocols, “401 Unauthorized Sip” and “401 Unauthorized” have similar error codes and general meanings. The differences between the two are broken down as follows:

  • Protocol: The 401 Unauthorized error is an HTTP status code used in web-based communication, the SIP 401 Unauthorized error is specific to the SIP protocol used in VoIP communication systems.
  • Context: SIP 401 Unauthorized refers to authentication mistakes within a SIP session, which show a lack of authorization to continue. Unauthorized access to a website is indicated by the HTTP error code 401 Unauthorized.
  • Application: Real-time communication sessions are most impacted by 401 Unauthorized Sip, which primarily affects VoIP systems. Meanwhile, the 401 Unauthorized error appears when accessing web resources, including webpages or APIs.

For easy follow-up, you can see the summary table below:

Differences SIP 401 Unauthorized HTTP 401 Unauthorized
Protocol SIP protocol used in VoIP communication systems HTTP status code in web-based communication
Context Authentication mistakes within a SIP session Unauthorized access to a website
Application Webpages or APIs Real-time communication sessions

Causes Of SIP 401 Unauthorized Error

When authentication-related problems arise during the initiation of a Session Initiation Protocol (SIP) session, the SIP 401 Unauthorized error occurs. The following are some typical reasons why SIP 401 Unauthorized occurs:

  • Invalid identification: Entering the erroneous username, password, or domain information during the authentication procedure could result in providing inaccurate or invalid credentials. As a result of failing to recognize the credentials supplied, the server denies the request.
  • Invalid or expired credentials: SIP systems frequently need regular authentication changes to maintain security. The server invalidates expired credentials, which can cause a SIP 401 Unauthorized error due to outdated or revoked authentication information.
  • Unauthorized device or user: If the user or device is not authorized to access the system or registered, the server denies the SIP session request. Before proceeding, the user or device has all the required permissions and authorizations.
  • Issues with network configuration: Network configuration problems may result in a SIP 401 Unauthorized error brought on by routers, firewalls, or other network devices. Besides, the ability of the user or device to communicate with the server may also be interfered with by problems with network address translation (NAT) traversal.

Network configuration causes Sip 401 Unauthorized error

  • Registration timeout: To establish presence and authentication, SIP devices periodically register, however, if the registration process is failed or times out, a 401 Unauthorized error can occur. Network connectivity issues or wrong registration interval settings are reasons for this response.
  • Certificate expirations: An expired or incorrect server certificate might result in authentication issues when utilizing Transport Layer Security (TLS) for secure communication.
  • SIP ALG conflict: SIP Application Layer Gateway (SIP ALG) is activated on some routers, which can obstruct SIP communication and authentication, resulting in the Sip 401 Unauthorized error.

5 Potential Ways To Fix Sip 401 Unauthorized Error

Generally, detecting and resolving authentication problems can be made easier by comprehending their causes and putting the right solutions in place. You can attempt the following fixes to resolve the SIP 401 Unauthorized error:

Verify Credentials

Verify the username and password used for authentication once more. Ensure that they are entered accurately in the SIP client’s settings. Finally, you should keep in mind updating both the SIP client and server setups with the new credentials if they have recently changed.

  • Update new password: If the user’s password has been changed, ensure the SIP client and server are properly set up with the new password. Outdated passwords can cause failures in authentication.

Update new password to verify credentials


  • Check SIP Domain: Make sure the SIP client’s given SIP domain or server address is correct and matches the SIP server’s domain.

Refresh Credentials

Contact your VoIP service provider and ask for new authentication credentials even though you think the credentials are outdated or invalid. Then, change the settings of your SIP software or device accordingly.

Verify The Network Configuration

Check your network infrastructure to ensure it is set up properly for SIP traffic. Besides, ensure that firewalls or routers block no media or SIP signals. If you require assistance, consider speaking with an IT specialist or network administrator.

Troubleshooting For Registration

Changing the registration interval settings in your SIP device or software should solve the problem if registration timeouts are the cause. Furthermore, ensure there are no interruptions by confirming the network link between your device and the server.

Get Technical Assistance

You should contact the technical support staff of your VoIP service provider if you have tried every workaround and are still experiencing the SIP 401 Unauthorized error. They can assist with the problem’s resolution and give detailed advice based on their system architecture.


Common problems with VoIP communication systems include the SIP 401 Unauthorized error. Identifying the problems and putting the right fixes in place can assist in troubleshooting and resolving authentication problems. 

Users can fix the 401 Unauthorized Sip problem and take advantage of flawless VoIP conversation by checking and upgrading credentials, evaluating network setups, and contacting technical support as necessary. 

You should remember that a properly designed SIP environment not only avoids authentication problems but also improves the overall performance and dependability of your VoIP system.

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With over a decade of experience crafting innovative tech solutions for ecommerce businesses built on Magento, Jacker is the mastermind behind our secure and well-functioned extensions. With his expertise in building user-friendly interfaces and robust back-end systems, Mageplaza was able to deliver exceptional Magento solutions and services for over 122K+ customers around the world.
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