Hi @Solla-topee 

Thanks for your help. I have checked everything I could.

I am sure I have the wired-only model TL-PA. When I power it on, additional DHCP server appears on the network. Trying to log in with any credentials I receive a wrong password error containing a very specifi text which, when googled, is linked to TP-Link devices. When I remove the main unit from power, the DHCP server dissapears.

I also installed some TP-Link configuring app, which identifies both devices properly as TL-PA4010P.

Is there a possibility of some strange system software on the device? I never upgraded it and it should be factory-default.

Thanks for your help,

Borut 

  @Solla-topee

Hi.

No wifi powerline extenders; also no other TP-Link devices in the house.

I have double-checked - when I connect my 'master' TL-PA4010P powerline extender to the network, I can connect with browser to the rogue DHCP device (Picture 1):

When I fail to log in a few times, the error message appears:

Also during that time the network name displayed in TSR is 'Primary_2' which I believe means I am connected to some network extender. And no connection to internet is established.

When I unplug my 'master' TL-PA4010P powerline extender from the network I can no longer reach the device with browser:

After resetting DHCP settings on my computer I get connected to the internet and the network name displayed in TSR also changes to 'Primary' (directly without some network extender).

And yes, it does cause trouble on the network. Various DHCP devices, probably when occasionally restarting, get address from the 'rogue' lower DHCP pool. As the rogue DHCP network is on 192.168.0.X and my router's network is on 192.168.1.X, I thought if disabling the 192.168.0.X (supposedly TL-PA4010P) or at least changing it to a higher scope (e.g. 192.168.3.X) would solve my problem. But I can not access that rogue device on the 192.168.0.1 address.

Thanks for your help again.

Borut