All devices lose internet connection when connecting work laptop to tailscale VPN with KPN Box 12

​I got the issue today. I will try to describe everything

I switched to the simplest setup 8 days ago: Kpn Box 12 connected to fiber box. All my devices connect to Kpn Box 12 wifi
I have normal dual-band wifi, and I have extra wifi enabled with separate SSID for 2GHz and 5GHz
My laptops use 5GHz one

8 days it worked well, with no issues

Today I opened my working laptop that started connecting to corporate tailscale vpn, and internet stopped working for all my devices. It didn't work for 5-10 minutes and then started working

I started `ping 192.186.2.254` and `ping 8.8.8.8` on both personal and working laptop soon after internet dropped. I started connecting my 2nd laptop with ethernet cable, but wasn't able to do it on time. I suspect it would have the same issues, I have some screenshots with pings that prove it

In the kpn box 12 logs I see that internet dropped without any logs, then my devices disconnected from wifi (cause no internet), then `Connection has been terminated: remote station is not answering to LCP Echo requests.` and `Connection to the Internet has been terminated.(Reboot,Reconfiguration,forced termination)` and `PPPoE connection successfully established with user credentials.` that fixed the internet. You see my attempts to connect ethernet cable too
pings from working laptop

pings from personal computer:

Kpn Box 12 logs during the event

Now every time I connect tailscale, I see internet interruption.
It wasn't like this last 7 days
 

​

Happened today again when I turned on my computer. Again on all devices.
Then smaller downtime happened when I turned on tailscale

Turning on the computer (maybe tailscale on work laptop reconnected too, not sure)
Laptop, connected through ethernet

Computer, connected through wifi

And when turning on tailscale on working laptop
Laptop, connected through ethernet

Computer, wifi

I did reset on my kpn box 12 now and will stop using extra wifi (that gives me separate 2ghz and 5ghz SSIDs)

It works well now, will see in 8 days

I got a confirmation from 3 coworkers that they have the same kpn box 12, same software version `SGEJ1000060E` and the same problem
I suspect the problem was not in extra wifi feature

We don't recognise the issues you're describing, ​@krock21. What might help, though, is adjusting the MTU size to 1280. This is something you'd have to adjust in the VPN settings. I hope this works for you.

Thanks
Will try it next time I have issues

Tailscale configuration is managed by my employer

They said it is already configured to 1280 and it doesn't look like an MTU problem

Do you have any other ideas/suggestions?

I am afraid I don't have another suggestion. We do not block the usage of VPN. The common factor seems to be your work VPN. So it might be something in their configuration. I'd suggest you take this up with the IT servicedesk at work. Hopefully they can help.

My kpn box should have been updated this night(I received an email yesterday), but seems like something went wrong, because my software version is still `SGEJ1000060E` and I saw a couple of `Remote station is not answering to LCP Echo requests` in the modem logs at night

Today I was able to capture small outage (3 minutes) when I turned on tailscale. I downloaded PingPlotter for it, it should do traceroute and plot pings to every hop

I don’t see any log messages in kpn box 12 at that time

I did it on 3 devices:
Working laptop, connected through wifi and connected to tailscale:

Personal computer, connected through wifi:

Personal laptop, connected through a cable:

It looks like the update failed then, ​@krock21. If this keeps happening, my advise would be to reset the modem. This increases the chance we'll be able to push the update.

I did modem reset 6 days ago and changed nothing since then (except wifi SSID)

We'll just have to wait until an update sticks, then. Another reset of the modem might help, but still is no guarantee.

As for the loss of internet when connecting to tailscale: I honestly have no idea what this could be. Did you contact your IT support yet?

Yes I contacted IT support and we contacted Tailscale about it

Could you please provide details of 1st hop? `195-190-228-10.fixed.kpn.net`
Is it fiber box? Is it a single thing for floor/building/district?

This is your WAN IPv4 adres 195.190.228.10, i hoop that you wil not be a victim of DDOS attack in next days, because you put your own ip adres on a public forum.

No, it is not

What is your IP adres from site whatismyip.com

nslookup 195-190-228-10.fixed.kpn.net
Server:  security.cloudflare-dns.com
Address:  1.0.0.2

Non-authoritative answer:
Name:    195-190-228-10.fixed.kpn.net
Address:  195.190.228.10

Not 195.190.228.10

Then it is the IP adres of the POP station in jouw neighborhood.

That's very good to hear, ​@krock21!