I have an existing VPN profile on my iPhone which connects to my Vigor 2866.
This has been working perfectly however over the past couple of days when I connect, no traffic is passed through the VPN connection. I am able to ping devices on my network when connected but nothing else, Apps do not work.
Updated to iOS version 16.0.3 recently, wonder if that's the issue?
I'm using an EE sim.
Anyone else noticed an issue on a similar setup?

This report is of IOS VPN data not always travelling down the tunnel, when it should.

Of course, if the traffic is actually destined for the Internet, it would still work - but not be encrypted. If it's intended for a device at the VPN endpoint, it would fail, if the data was sent out in the wide-blue-yonder instead...

So after much research and talking to both EE and Apple the issue appears to be due to EE's network using IPv6 whilst my broadband connection uses IPv4 hence some sort of routing issue and no traffic being passed through the L2TP tunnel. EE told me that they don't officially support any kind of VPN connection over their network, but it's always worked on other mobile networks that I've used.
This can be fixed by editing the APN on your phone to only allow IPv4, however this is not possible on an iPhone, unless you have a Mac computer and push a configuration change using Apple Configurator, see this blog for an explaination, https://blog.dotsmart.net/

I didn't have access to a suitable Mac computer to push a new config so I've discovered a new VPN named Tailscale which uses WireGuard, thanks to the author of that blog. https://tailscale.com/
I installed the Tailscale app on my Synology NAS and iPhone, this handles the VPN connection perfectly with no issues over the EE network.