ISP Sky Broadband UK Promises to Fix Router WiFi Calling Bug
Internet provider Sky Broadband has promised customers of their service, specifically those connecting via the latest ‘Sky Max Hub‘ router, that a fix is on the way for a long-running bug that appears to be preventing users from being able to use Wi-Fi Calling when on their home network.
Most people probably already know this, but Wi-Fi Calling (aka – VoWiFi) enables consumers with a supporting Smartphone and mobile operator to harness their home broadband connection or other WiFi service to make mobile voice calls, instead of using your mobile (2G, 4G or 5G) network. The feature is extremely useful, particularly when away from a good mobile signal, but support can be patchy between different networks and devices.
However, some customers with Sky’s Max Hub router have been complaining (Sky’s Forum), at least since around early December 2024 (or possibly earlier), that they’ve been unable to get Wi-Fi Calling working at home. So far as we can tell from the feedback, this issue appears as if it could be down to Sky Broadband’s relatively recent implementation of MAP-T based IP address sharing (details).
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Sky were one of the first UK ISPs to adopt MAP-T last year, which is generally an improvement compared with the much-maligned Carrier Grade Network Address Translation (CGNAT), but it’s not perfect and can sometimes conflict with certain online services.
In this case, MAP-T also appears as if it may have caused problems for some customers with Wi-Fi Calling, which is supported by the fact that those who have made a request for the feature to be disabled were able to get the service working again. Unfortunately, this fix doesn’t seem to last, and some users have reported that it returned a few weeks later. Sky are aware and working on a fix.
Sky’s Community Manager, Kev, said:
Thank you for bringing this problem to our attention.
I’d also like to thank you for your perseverance and patience whilst we work through this technical issue.
Our support teams are working on a solution, and we will be updating customers connections automatically.
So that everyone has access to the most recent update, I’ll be marking this post as the answer. It doesn’t mean that the issue is resolved, it confirms that we’re working on the solution.
Sky’s statement was posted nearly two weeks ago and customers have yet to see a fix being applied, but hopefully they won’t have to wait too much longer. In the meantime, those who want to try working around the issue could try using Sky’s VPN request form, which relates to an MTU tweak that when applied may be able to resolve the issue, at least temporarily. More advanced users can also try applying this themselves (details here).
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on X (Twitter), Mastodon, Facebook, BlueSky, Threads.net and Linkedin.
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That issue has been going on alot linger than December 2024. You can add at least another 2-3 years to that. It is exactly why I was able to leave Sky early contract because wifi calling was not working on new iphones I purchased from them. They tried all kind of tricks which had nothing to do with the faults. But could not resolve it. There was also hundreds of complaints on the forums. So this is not an isolated issue. They also have issues with VOIP services. It’s that bad that three of my customers are now moving away as we cannot get this resolved.
It has been going on in Italy too since the very beginning of MAP deployment, but as in Italy WiFi calling was authorised and immplemented only starting 2022/2023 there have been delays in detection too by Sky… it is still not working there either.
Oddly enough it seems to be working here on Three on my Pixel 8, at least it says 3 WiFi calling if I switch to airplane mode.
I did suffer from the MTU issue for work VPN though, but that was resolved by setting it on the laptop
From what I can tell from reading this article, it seems like Sky made some changes to their network that are interfering with path MTU discovery, which relies on ICMP messages to work correctly.