NetGear jwnr2000v2 When connected via LAN cuts the speed. What to do?

Question

NETGEAR

I've been struggling with this problem for a year now. When connecting any device via LAN, the router cuts the speed up to 20Kb / s. At the same time, all devices connected via Wi-Fi work normally, the speed is slightly less than the declared one (Wi-Fi costs). Provider Beeline (l2tp), when connected to another provider, everything works fine. At what it all started when translating to l2tp, before that I worked normally on the beeline for 1.5 years. And as I understood climbing the network, this is not only my problem. In Beeline technical support they send me to NetGear technical support, in turn Netgear sends me to Beeline. Just a vicious circle. Tell me good people what can be done.

Answer 1

Change the router, obviously.
*or play with the MTU \ MSS settings (but, it seems, your model just does not allow this)

Answer 2

It's just that suddenly someone will suggest a solution, and I already thought about replacing the router and changing the provider.