VoIP Issues Caused by SIP ALG

SIP ALG setting on your router and how to turn off the setting to solve VoIP Issues.

HOT JANUARY SALE

HUGE £30 OFF EVERY PHONE
Banish the cold with our Hot Phone Sale! £30 off EVERY phone purchased upfront in January 2026 for new customers - use offer code JANSALE26.

SIP ALG and VoIP

SIP ALG is a tick box setting on most routers that cause stability issues with a VoIP Phone system.

By default many routers come with this ticked, but it‘s a simply task to solve. Just login to your router, look for the SIP ALG tick box, untick it, save and your issues will probably be resolved.

Symptoms of SIP ALG

More often than not, SIP ALG will highlight itself by causing the following symptoms:

Calls dropping when another all comes in.
Only one phone working
Problems transfering calls
Problems with people not being able to hear you

Why does SIP ALG cause the issue

The setting causes your router to send the packets to a single point for all the VoIP traffic. But if you have more than one device, the router doesn‘t know which device to send it to, so it chooses at random where to send the voice traffic. This causes the voice traffic packets to go to the wrong device and result in packet loss.

Disabling the setting on your router will resolve the issue. For some assistance on a technicolor router, read our guide.

Updated on 25/05/2024 by David Wood

As senior cloud solutions architect at TelephoneSystems.cloud, with a degree in computing, I bring over 29 years of extensive experience in cloud technology.

Back to Troubleshooting

More handy troubleshooting guides

Network Troubleshooting VoIP Phone Systems

VoIP Issues Caused by SIP ALG

POE Switch Issues with VoIP

Virgin Media and VoIP Issues

Sky and VoIP Phone System Issues

Wi-fi Troubleshooting with VoIP Phone System

Troubleshooting VoIP Phone System over 4G and 5G

Troubleshooting VoIP Phone System with loss of power

Disabling SIP ALG on Technicolor Router Guide

Setting up your Firewall Setting for VoIP

Mobile phone power saving settings and VoIP Issues

Having issues porting your number to a VoIP System

Starting Troubleshooting your VoIP Phone System

Experiencing call dropping on VoIP Phone System

Experiencing quiet calls on VoIP Phone System

All Troubleshooting Guides...

Why We Are Different

No Crazy Contracts

Fed up of a deal always looking to good to be true? Since we are contract free, you always pay the price on our website, ensuring no hidden price rises. Pay the same as a new customer every month!

Reliability you can trust

We guarantee 99.9% uptime backed up by our SLA on our robust UK dedicated VOIP platform in conjunction with CISCO & Openreach. Monitored and managed 24/7.

Fanatical about support

All are calls are answered in less than 10 seconds here in the UK, why not call us now and find out how friendly our team are!

Free configuration & support

All our VOIP systems are configured in the cloud, so there are no configuration, installation or support charges. Our phones simply auto install when plugged in. Free Support

Learn more about our VoIP phone system...

App &
Teams

"Honestly, this company was incredibly easy to deal with and extremely helpful. The online ordering process was straightforward, and the staff were always on hand to help. We moved all 13 telephone numbers away from BT after BT Local Business completely messed up our accounts, and the transition couldn’t have been smoother. Number porting, invoicing, and online payments were simple and hassle-free. The equipment was true plug-and-play — a total breeze. Best of all, we now have one clear, straightforward bill, and there’s always someone available when we need support. Absolutely brilliant service — love you guys."
By Audley End Chauffeurs

"I have moved two companies that I am involved with to this company and they have been more than helpful with installation and any further questions that we have had. I couldn't recommend them enough."
By Fenton Barns Nursery Ltd

"Switched to a new phone system and the whole process was very easy and was half the cost of the previous supplier! Would highly recommend"
By East Radnorshire Care

"Fantastic, many thanks"
By Marple Ltd

"Open and transparent company, first class service and advice to our telephone system"
By Plusfile+ Limited

"Highly recommend, Telephone systems have been very helpful and quick to respond with any questions or help we need. Special mention to Josh for setting getting us started."
By DB CHIRO LTD

"The guys are a pleasure to deal with. Literally nothing is too much trouble and you are dealing with real people in the UK! That alone is worth double what they charge anyway! I will be back for more connections for other companies in the future, thanks again everyone."
By Mc Mennis

"We have been fearing VOIP phones as we live in a rural location with no mobile signal. The condition of our BT landline is so bad that we are no longer able to hear customers clearly and after nearly ten years with no help from BT or Openreach and after much research we chose Telephone Systems. We were also nervous as we use Starlink for our internet connection."
By ROB BLACKMORE HEATING SERVICES

"I decided to change away from BT and move to Telephone Systems. Everything has been so easy and straightforward with them."
By House of Blinds Ltd

"Used them for many years now they look after all our phone systems / software like office365 licences and should we ever have a query or a technical issue we need help with they are on the ball ASAP. :)"
By Elsby Associates Ltd

"Really helpful and guide me through remote phone access."
By House of Mortgages

"Very quick and efficient customer service - excellent people"
By Canonical Tutors Ltd

"Always helpful, always professional and never let me down no matter how difficult my requests. Brilliant service"
By Wendy

"Very competitive pricing, great service nothing is never too much trouble. Thanks for all your support."
By Totally shutters Trading Ltd

"The team are very helpful and they react quickly to resolve any issues that may occur. The system works anywhere that there is an internet connection."
By Able Property Services Ltd

"Easy to work with and always quick to reply. Highly recommend."
By Rob Lapthorn

"Great service from inception, support team is very quick to respond and assist with any queries or issues that we have encountered. Would recommend"
By Jake

"Easy system to set up and operate. With first class after care"
By Jolly Roger Cars

"The system works very well for us, especially when working remotely. Some of the newer facilities in particular, such as the e-mail voice messages are great. I can just send on to the right person."
By Royal Institute of Navigation

"This company is amazing, no problem is ever too small. Special shout out to Josh who always delivers. Prices are reasonable and the service is exceptional. Would highly recommend!"
By NP

"Great system, very easy to use and customer service is alsways very helpful and quick to respond."
By Modus Personnel

"My last provider was three times the price of telephone systems, also telephone systems the service is better as well. I would definitely recommend for your VoIP service"
By Dirty Marks Cleaning Services

"Very happy to use Telephone Systems.Cloud. They have been a telecoms provider of ours for a number of years and have been great, no complaints whatsoever."
By The Tasting Quarter

"Josh has been wonderful, from the very beginning, he's always on hand to help with any technical issues he even suggested a resolve for my systems that worked perfectly. He's always there on the end of the phone with a last minute message that I need setting up, never complains, always has a respectful happy manner.... HIGHLY RECOMMEND."
By LA PD Gas

"Great company, good prices and very knowledgeable about there product."
By M W Truck Parts LTD

"Josh who normally deals with my problems if we have any and has always been excellent at sorting things out for us 10 out of 10"
By Martins Electrics Ltd

"System for VOIP with a local phone number is working very well for our village residents. We use it for organising local transport trips. Our elderly residents hate mobile numbers ringing them but to have our own local telephone number gives them confidence to answer and receive our calls."
By Barlaston Volunteers Car Scheme

"Superb company, we have been using these guys for a number of years and they are excellent."
By Virtual Flight Experience

"Very good no issues always available to talk always helpful."
By J and D

"We're a small business and needed to change to VOIP before the landline switch off. I made the mistake of filling out an online form and was bombarded by VOIP firms, who wanted to sell us 3-7 year leases! Found TelephoneSystems online and was super impressed by their refreshing approach to the whole shebang, namely a monthly rolling contract, no exit fees. Simply outstanding."
By Chau Digital

"I've used Telephone Systems .Cloud for my business for around 4 years never had a problem always been helpful and helped with the expansion of my business without costing an arm and a leg"
By Scootdog

"Good service and great customer service."
By Equity Charitable Trust

"We have in the past had experiences with a number of telephone system and call providers..............all of them, regretfully, bad!"
By TA Associate Services (Lincs) Limited

"Brilliant service provided."
By Medical 4 Drivers Ltd

"We have used Telephone Systems since our company started and have nothing but praise for them. I have personally dealt with Josh Barnett several times and he has always gone above and beyond to resolve any issues we have had with our phone set up. Would highly recommend this company to anyone needing a flexible and reliable provider and service."
By The Property Ladder Group

"We have been fearing VOIP phones as we live in a rural location with no mobile signal. The condition of our BT landline is so bad that we are no longer able to hear customers clearly and after nearly ten years with no help from BT or Openreach and after much research we chose Telephone Systems. We were also nervous as we use Starling for our internet connection."
By Rob Blackmore Heating Services Ltd

"Been with them for 5 years now and absolutely excellent service every time, especially from Josh. Really pleased."
By Total Brands Ltd

"Very friendly and helpful company, with keen prices."
By The Saddlery Shop Ltd

"All my experiences with Telephone Systems has been positive, I have recommended them to other companies and will continue to do so. I have dealt with Josh and a number of people on their support team, and all of them have been extremely efficient and responsive."
By Northlight Studios

"We've been using telephonesystems.cloud IP phones for a couple of years now and have always found the system to be reliable and cost-effective."
By Human Workspace

"Have used this company since 2020 and have found them knowledgable, fast and great value. Josh has been fantastic to work with and easily and effortlessly works through any issues we've had. Would highly recommend them to any small business looking for a reliable system that's good value and with easy point of contact."
By Holley Protect Limited

"Amazing customer experience, highly recommended!"
By Pollyanna Fine Bone China Ltd

"We switched to the team during Covid and they have been consistently fantastic. They help with clear, consistent information, solve each request we make and always help quickly and correctly. They are affordable, friendly and personal. Highly recommended"
By Butlers Chartered Accountants

"I have been using the voip service from Telephone Systems for 3 years now, I have never had a single issue with their app of service."
By The Britannia Chauffeurs

"Great product but more importantly great service and support always from Josh & the team. Thank you guys!"
By Let Correct

"Excellent service, great pricing, friendly team."
By Lucie Blackman Trust

"Always been great and competitively priced"
By Norwood Finance Ltd

"We've been using Hosting Systems for many years and very happy with their service; we've recently adopted a VOIP phone system that is working very well. Support is excellent. Highly recommended!"
By Robinson Wire Cloth Ltd.

"Telephone Systems made it very easy for my business to switch to a digital phoneline and ensured I didn't lose my old number. Thank you."
By Josh.biz (UK) Limited

"Having used Systems.co.uk for many years for email and website services it was only natural to approach them when we decided to switch to a cloud based phone system. All I can say is hats off to them, the process has been seamless. I have no hesitation in recommending them wholeheartedly to anyone looking for a trustworthy partner for these sort of services."
By Nirvana Enginnering

"Can't recommend this company enough. Friendly, helpful, knowledgeable and all at a competitive price. I won't use anyone else as a business telecoms provider."
By Red Electrical Distributors Ltd

"Great and quick support service - always!!!"
By Cumbria Action for Sustainability

"We have used this company for 3.5 years and are delighted with the product and customer service are always there to help."
By Paul Chillingsworth Homes

"A very friendly and helpful service."
By Base Creative Ltd

"Our experience with Telephone Systems.Cloud has been nothing short of brilliant. Since joining them in November 2020, we've noticed significant improvements in our communications. The transition to their system was impressively smooth, and the support from Josh has been outstanding – he's a top-notch professional and always ready to assist. I highly recommend their services for anyone looking to upgrade their telecommunication systems. The reliability, user-friendly interface, and exceptional customer service make them a standout choice in the field."
By Queensborough Group BB

"About on year ago I took a decision that I have been trying to take for about ten years. The decision? To move my small family business to VOIP phones and hope that they now work OK (2022!) , with good support and fallback systems. Well I did not need to worry .... I chose a local company with a good reputation and off we sailed. The experience with Telephone Systems has been truly faultless and we have been handled with kid gloves all the way through. The system is excellent on call quality and we have flexible access to the same fixed monthly call charges via user mobile phones too. If you are looking at hosted VOIP service do give this company a chance to quote. Excellent service supporting our self install, no "hard sell", simple, fair and transparent capped pricing and no long term contract. We don't need anything else!"
By Endon Services Group

"TS.C are an open, honest and professional phone system supplier, very supportive throughout the whole process of replacing an old VoIP system for a new version. As a result, the swap from old to new was as seamless as these events can be. We are very pleased with the new system and its feature rich benefits, ideal for our company."
By Courtney-Thorne Ltd

"Excellent company to deal with. Service is really good. Pricing is very keen and no long term contracts. TelephoneSystems.cloud really do standout from the crowd in the telephone service industry. I use them for all my businesses. Highly recommended, you do to."
By Solent Renewables

"Great service, pleasant helpful staff and all the equipment arrived quickly and correct."
By IFabs - Mark Collishaw

"Staff are excellent, informative and experienced in talking through options and then came back to check requirement as process continued - altering the type of router to provide a better fit. I am not sure there is anything I would improve, which perhaps explains why I keep coming back to the company for all my 'systems' needs."
By DSJB Associates Ltd

"Excellent service and very knowedgeable staff quickly guided us through a complex ISP change to them. I cannot recommend them more highly."
By Worthington Aviation Ltd

"5 Star Service - Swift, Courteous, and hassle free. Thanks for your support."
By Lloyds Contracts Ltd

"Excellent service - there's an actual human on the other end of the line, imagine that! : )"
By Mr JWW

"Delightful people and company to deal with. Brilliant service and superb after-sales support."
By 10outof10 Productions Ltd

"Early days, but painless migration from Vonage for my business, and refreshing to actually be able to speak to humans again, to sort out any minor niggles or help with new system. Very impressed and look forward to a long partnership."
By Trusted Directory Services Ltd

"Having had lots of trouble with an Internet Provider stepping up payments I am now in a much better position. Always know what you are paying for with Telephone Systems, clear billing and no hassle with the change over."
By Irene Moran

"Simply a fantastic company that employs actual humans you can speak to, NO bots, NO script reading call handlers, REAL people! Not only that, these wonderful beings can even resolve any issue without passing you to another department or putting you on hold for hours at a time. From sales to billing to technical support, they provide an outstanding service. I highly recommend this company!"
By Rebekah Lowther

"Everyone at telephone systems go above and beyond, would highly recommend to other businesses. Seamless provider transfer and install of new fibre to premises. Telephones are also a great upgrade for our business. The online webex app is great for times when we are out of office & the pre programmed messages / out of office have made things a lot easier for us! Thanks to everyone I’ve dealt with at TSC"
By The Dentist @ Tupsley

"I found telephone systems on line and was attracted to the very reasonable price along with no contract length commitment. The fact that they don't feel the need to tie you in to long contracts, tells me they are confident that what they offer is competitive. But great service too, no long wait times waiting on help. We are only a small company with 5 x phones but have made a decent saving"
By Shrink Polymer Systems

"The help I had from the staff here was impeccable, after 5 years being ripped off by another company Alistair helped us through the process of changing our system easily and the savings this has made to our company has been such a financial improvment to us being a small company, I wouldnt hestiate to recommend this company to anyone. We here at SLM are delighted with the service we have been given."
By Stevens Lettings and Management Services Ltd

"The telephone system we now have in place is perfect, great value and excellent service. Just wish we'd have done it sooner......highly recommend!!"
By Amy Davies

"TelephoneSystems made what had previously been a torturous and time consuming process so very straightforward and transparent."
By Brenuus

"A great phone system with apps that work so you can take calls from anywhere. Help centre is great too they are always happy to help me."
By Charlotte Vincentt

"Switched from extremely expensive BT to this system and I wish I had known about this years ago."
By Driverhire Chelmsford & Harlow

"Superb service, excellent support, and you actually get to speak to the same human being each time! Highly recommend!"
By Colin Hallmark

"Took less than a day to get setup with a softphone system, really helpful staff, I highly recommend this company!"
By So Simple IT Ltd

"Great company excellent customer service would highly recommend"
By UK Utility Solution Provider Ltd

"I don't often leave reviews, but we've been with these guys for over a year and the service has been pretty much flawless. Such a change from our previous suppliers with whom there were constant problems. This service is also a fraction of the cost. Highly recommend!"
By Jonny Arbon

"Superb service, excellent support, and you actually get to speak to the same human being each time! Highly recommend!"
By 3nine Communications

"Telephone Systems.Cloud is one of the nicest companies that I have ever had the pleasure of dealing with. The staff are charming and impeccably mannered. They are technically brilliant and absolutely focused on the needs of their clients. I struggle to find anything that could be improved upon. I would have no hesitation whatsoever in recommending them."
By Andrew Smith Funeral Services

"We needed a business phone solution for our business, this has been EPIC, all pre configured, easy plug and play, it has brought our business together - 100% awesome !"
By 2nd Generation Facades

"seamless service from start to finish, offering a personal & friendly yet extremely professional service. highly recommended :)"
By Minshall & Co

"We would recommend you to anyone, frankly. You've been professional, responsive, friendly and obliging. After running a terrible gauntlet with a ("the") major telecoms company and reaching the end of our tether, you have been a breath of fresh air. It was such an easy transaction! Uncomplicated, quick and exactly what we needed - seriously, we've been so impressed with you we can't recommend you highly enough."
By Gewefa Uk Limited

"The service received so far has been outstanding! Nothing is too much trouble and any requests are dealt with promptly. In these difficult times it is refreshing to see a proactive company working so effectively. Keep up the good work!"
By European Power Systems Ltd

"I was initially concerned that I was switching to a small company, for something as important as our telephone service. There is something strange about being in the clutches of a mega-corporation such as BT.... awful experience, but hard to leave! I need not have worried. Superb experience with yourselves, from setup to usage. Also, you guys have a sensible, fair, straightforward and competitive pricing system. Keep up the good work, because the telecom industry needs providers like you."
By Powercut (Wales)

"I have to say that you guys are a breath of fresh air in the telecom world. "
By Powercut (Wales)

"Phone are good quality and the customer service is excellent"
By Bowella Recruit

"Installation was quick and easy and the system is working well for us"
By Labelcraft UK Ltd

"Good service. Quickly set up and cost effective, Very helpful support and sales staff, Quick, cheap, efficient."
By Invicta Property Maintenance Services

"Excellent product and service"
By Tarpey Woodfine Architects

"The line is crystal clear and far better quality than my mobile or any other app. Excellent Staff....really good to just go online and get an immediate response in the chat screen."
By Ethos Education Limited

"I would like to say how happy I am with the product that I purchased from your company. I would also like to particularly mention my appreciation to Josh in your Support Department. Throughout the whole process of setting up, Josh has been brilliant and so helpful and I hope he receives recognition for the outstanding customer service that he has provided to me. He is a credit to your company!"
By David Simpson

"Excellent in every way"
By Devcomp Ltd

"Fantastic company. Really straightforward to work with. We have been using the phone system for a few months now and it's been exactly what we need as a small business and very affordable. I wish all telecoms companies were like this!"
By Ladyhall Ltd

"Great service from the staff who really took the trouble to make sure that we were set-up properly. On the switch over day the numbers from our old supplier were ported over exactly as planned by Telephone Systems - to the very hour!"
By Bailey Solutions Ltd

"Couldn't be more helpful, helping us set up our new system. Really easy to use and straightforward to install with NO previous knowledge. "
By Ladyhall Ltd

"Really helpful staff helping me to get set up, with no problems at all Thanks Guys!"
By Actiman Ltd

"Very smooth implementation, great support when needed (although this has not been very much) and clear lines. All round, very impressed."
By Ripple Recruitment Ltd

"Do yourself a favor and switch your physical phone line to cloud"
By Removals and Storage Experts

"I need to keep my phone number when moving exchange, these guys made the transition as easy as I think it could get! A few teething problems where sorted with patients and speed. Always at the end of the phone to answer questions from this non techy Luddite! Compared to the same service with BT we saved £30 per month "
By Forever Green Florist

"Excellent pre and post sales service,your team have been outstanding even to a small user like us - thank you"
By Recur Global Ltd

"If any of my contacts are looking for a cloud based telephone system, I can't recommend these guys enough!!No contract, great prices but most of all outstanding customer service, nothing is too much hassle for them. Thanks guys you have made the process v..."
By DBS Processing Ltd

"Very pleased with the service from start to finish. The whole process was quick and simple. Phones were very easy to set up and any queries we had were quickly answered. Wish we had swapped over to a VOIP system years ago. The phone itself is very good quality and the line is clear"
By Rebus Training Ltd

"Spoke to a lot of suppliers and found Telephone Systems were the most straightforward to deal with and in their pricing. Set up was really simple and the team jumped on anything that we wanted to customise straight away with no hassle. Really pleased with our choice of supplier!"
By NSBV Projects Ltd

"The team has been extremely helpful. What is important for the user - quick replies. Excellent service. "
By RBWTL

"We've worked with Telephone Systems for a number of years. Really please with the telephone and the service. They've always been willing to help if we've need to add or remove users etc. The VOIP system has worked extremely well for us as we've expanded and moved office."
By Flowbird

"I have used Hosting Systems for many years and found them to be highly professional and helpful. This was particularly evident when we decided to go for a Voip system which turned out to be a complex challenge to provide exactly what we wanted to achieve."
By Anderen Ltd

"What a lovely and dedicated team! Whatever the issue they will go beyond to make your calls happen."
By Go Nurse

"The telephone system provided for our client is excellent. It was easy to order, to install and has been easy to add to since. Highly recommended and with the right connectivity it has been a fantastic update for the business in conjunction with their move to new premises. Call quality is excellent! More than happy to recommend."
By M&M Technologies

"Excellent service; fast, polite and informative. The system has modernised our telephone setup and is allowing us to deal with calls from our customers more efficiently."
By Party Shop Supplies Ltd

"I knew we were being limited by our standard phone system, but had no idea how to transfer to a cloud based system The team explained and handled the move perfectly. Incredible the difference it has made to our team and clients"
By Nexus Dental Laboratory

"Brilliant service, friendly staff. I was up and running in a few hours unlike other providers "
By KMB Storage

"We upgraded to the cloud system when our telephone system failed due to a power cut, the team were fantastic! Within the day we were up an running again and soon had the full system in place. Not only do we now have a more efficient, reliable and flexible telephone system but we really are saving money on phone bills. "
By Freedom Ltd

"Great service and very helpful just what I needed and was up and running in a hour"
By Dog Section

"After the initial trepidation of moving over from BT I can honestly say it's best thing we have done, easy installation, easy operation and great additional features all in all very happy"
By Penkhull Service Station

"Great superb quality system, at a very affordable cost. I can't rate highly enough. So much functionality for your gbp. Easy to appraise costs on the website, smooth effortless installation and integration. Superb back up from the team @telephonesystems.cloud"
By Total Image Solutions Ltd

"Very Good System, does pretty much what it says on the box, best feature for us is the remote office facility. Great!"
By Goldstraw Associates T/A 21st Century

"This is technology that really WORKS. The call quality is excellent, the convenience is excellent, and yes folks, you can use this anywhere you have internet connectivity or cell phone service. Take a call from Stoke in Western Canada and there is no lag; you might be taking a call from the office door. Plus you get the approach to customer care and relations: friendly, unflappable"
By Counselling People

"Really good service, system is easy to use, we save £250 per month compared with our old system."
By The Lyme Trust

"I cannot rate your service high enough. We were incredibly sceptical to begin with, based on the massive cost savings but since having the system installed, I can safely say it is the best thing we have done so far this year. Not only is the system so much more flexible, but the financial gain is staggering."
By NuPrint Lithographics Ltd