That's a problem of the Pirelli router.
Reported very early, also in Austria where they use the same router.
There's still no fix in any firmware. And I think there will be no fix, as the problem occurs since release.
You have to switch to the Motorola routers or use your own device.
I'm a big fan of the Pirelli device, but in this case it is shitty.
It should look like this, but it doesn't 😉
You'lle have problem with steam, but it could also occur with emule or ingame server search.