--- title: SIP ALG and why you may need to disable it description: SIP ALG is found on the majority of routers and it attempts to resolve potential SIP issues by modifying the data packets that make up the call traffic. image: https://www.cedartelecom.co.uk/hubfs/Act3%20child/images/Blog/Business-Telecoms-and-Business-Internet-Insights.webp --- [![Cedar Telecom](https://www.cedartelecom.co.uk/hs-fs/hubfs/Act3%20child/images/Cedar-telecom.webp?width=150&height=46&name=Cedar-telecom.webp "Cedar Telecom")](https://www.cedartelecom.co.uk/) [![Cedar Telecom](https://www.cedartelecom.co.uk/hs-fs/hubfs/Act3%20child/images/Cedar-telecom.webp?width=150&height=46&name=Cedar-telecom.webp "Cedar Telecom")](https://www.cedartelecom.co.uk/) - [Why Cedar?](https://www.cedartelecom.co.uk/about) - Products - [Data](https://www.cedartelecom.co.uk/data) - [Broadband](https://www.cedartelecom.co.uk/data/broadband) - [Ethernet Fibre](https://www.cedartelecom.co.uk/data/ethernet/ethernet-fibre) - [CRM Integration](https://www.cedartelecom.co.uk/crm-integration) - 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SIP ALG was intended to resolve specific issues that may be encountered when making calls over the internet. It attempts to resolve issues by modifying the data packets that make up the call traffic. SIP ALG is found on the majority of routers and firewalls and some have it turned on by default. However, SIP ALG can often actually end up doing the reverse of what is intended and actually introduce problems to your setup. SIP ALG can modify the data traffic that contains the call data and can effectively corrupt it by removing information that the system needs to work. The problems can be anything from phones not registering, not receiving calls or not being able to transfer calls. ##### How do I turn off SIP ALG? The method to turn SIP ALG off depends on the make and model of your router or firewall. Most devices have a web interface that can be used to turn SIP ALG off. The instructions for turning it off can usually be found in the user manual for the device. If your device does not have a web interface there may be other ways to turn SIP ALG off, for instance via telnet. Alternatively you should be able to find the way by searching the internet for instructions for the particular model you have. However some manufacturers have hard coded SIP ALG to their device's and it cannot be turned off. In this last scenario the options are limited but there may still be a way to get round the issue. [Contact us](https://www.cedartelecom.co.uk/contact) and we will be happy to discuss the issue. SIP ALG can also be referred to as SIP Passthrough, SIP Helper, SIP transformations or SIP enabled. - Recent - Topics - Archive Recent Topics - [News (21)](https://www.cedartelecom.co.uk/blog/tag/news) - [Business Ethernet (8)](https://www.cedartelecom.co.uk/blog/tag/business-ethernet) - [VoIP Phones For Business (5)](https://www.cedartelecom.co.uk/blog/tag/voip-phones-for-business) - [Business Telephone Systems (4)](https://www.cedartelecom.co.uk/blog/tag/business-telephone-systems) - [Remote Working Solutions (1)](https://www.cedartelecom.co.uk/blog/tag/remote-working-solutions) Archive - [September 2026 (2)](https://www.cedartelecom.co.uk/blog/archive/2026/09) - [August 2026 (2)](https://www.cedartelecom.co.uk/blog/archive/2026/08) - [July 2026 (3)](https://www.cedartelecom.co.uk/blog/archive/2026/07) - [June 2026 (2)](https://www.cedartelecom.co.uk/blog/archive/2026/06) - [May 2026 (2)](https://www.cedartelecom.co.uk/blog/archive/2026/05) - [January 2026 (2)](https://www.cedartelecom.co.uk/blog/archive/2026/01) - [December 2025 (2)](https://www.cedartelecom.co.uk/blog/archive/2025/12) - [November 2025 (2)](https://www.cedartelecom.co.uk/blog/archive/2025/11) - [August 2025 (1)](https://www.cedartelecom.co.uk/blog/archive/2025/08) - [June 2024 (1)](https://www.cedartelecom.co.uk/blog/archive/2024/06) - [May 2022 (1)](https://www.cedartelecom.co.uk/blog/archive/2022/05) - [July 2021 (1)](https://www.cedartelecom.co.uk/blog/archive/2021/07) - [June 2020 (1)](https://www.cedartelecom.co.uk/blog/archive/2020/06) - [August 2019 (1)](https://www.cedartelecom.co.uk/blog/archive/2019/08) - [April 2019 (1)](https://www.cedartelecom.co.uk/blog/archive/2019/04) - [January 2019 (1)](https://www.cedartelecom.co.uk/blog/archive/2019/01) - [October 2018 (1)](https://www.cedartelecom.co.uk/blog/archive/2018/10) - [September 2018 (1)](https://www.cedartelecom.co.uk/blog/archive/2018/09) - [July 2018 (1)](https://www.cedartelecom.co.uk/blog/archive/2018/07) - [June 2018 (2)](https://www.cedartelecom.co.uk/blog/archive/2018/06) - [March 2018 (1)](https://www.cedartelecom.co.uk/blog/archive/2018/03) See all ### Subscribe by email Share this [Share on X](https://x.com/intent/post?url=https://www.cedartelecom.co.uk/blog/sip-alg-and-why-you-may-need-to-disable-it&text=SIP+ALG+and+why+you+may+need+to+disable+it) [Share on Facebook](https://www.facebook.com/sharer/sharer.php?u=https://www.cedartelecom.co.uk/blog/sip-alg-and-why-you-may-need-to-disable-it&t=SIP+ALG+and+why+you+may+need+to+disable+it) [Share on LinkedIn](https://www.linkedin.com/shareArticle?mini=true&url=https://www.cedartelecom.co.uk/blog/sip-alg-and-why-you-may-need-to-disable-it&t=SIP+ALG+and+why+you+may+need+to+disable+it) Previous story [← Moving Office](https://www.cedartelecom.co.uk/blog/moving-office) Next story [Cellular Ethernet →](https://www.cedartelecom.co.uk/blog/cellular-ethernet) ## You May Also Like These Related Stories [What is GDPR?](https://www.cedartelecom.co.uk/blog/what-is-gdpr) ![What is GDPR?](https://www.cedartelecom.co.uk/hubfs/Act3%20child/images/Blog/Business-Telecoms-and-Business-Internet-Insights.webp) [News](https://www.cedartelecom.co.uk/blog/tag/news) ### What is GDPR? 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