@Piyush_1 

Hi,

When it's convenient for you can you test what happens if you leave your OnePlus Nord phone disconnected from your Wi-Fi network for a day or so? Check if all the Unknowns with MAC address AE:84:C6:x:x:x still show up after the OnePlus Nord wasn't connected to your router for some time.

If the Unknowns with MAC address AE:84:C6:x:x:x go away if the OnePlus Nord hasn't been connected for some time, then go to the Wi-Fi preferences of your OnePlus Nord and check if the MAC address setting says something like "MAC is randomised". If so, then you might want to try if disabling MAC randomisation can solve your problem.

@woozle 

No try to understand the "One plus Nord" device is not mine, this list is not the list of clients,this list is the list of blocked devices, that's what I am trying to say and neither the other devices are. Also these devices are not real, these are like technical glitches which when occurs slow my wifi speed. When these devices are connected to my wifi it slows the internet speed.No one in my neighborhood have any One plus device. The only way to solve this is to block these devices and then reboot my router.

@Piyush_1 

Ok, now I understand.

However, the TP-Link router can't make up names like OnePlus Nord or Lenovo Legion 5i on its own. This must be coming from actual client devices and if there are no such models around then perhaps another client device that has had its name modified by the user.

Have you already tried changing the Wi-Fi password of the TL-WR841N and then re-authenticate all your legitimate devices, just in case someone was indeed abusing your Wi-Fi?

@woozle 

Yes I tried it also I changed the admin password so that if in case someone gets connected then it cannot change anything.

Is any of the wrong settings messing with the router ? Don't know that if the ISP is doing something wrong during router setup.

@Piyush_1 

Was that router provided to you by your ISP? What mode is the router running at? (check under "Operation Mode")

By the way, make sure the "Guest Network" is either disabled or, if it's enabled, then make sure WPA/WPA2 security with password is configured for it.

@woozle 

The router is mine and was not provided by the ISP. The operation mode is:- Wireless Router. Also guest network is disabled.Also I noticed that like the devices that I showed to you I can also see another ghost router like it. See the picture below 

@Piyush_1 

I can't tell what exactly is going on with your router, but it seems to me that somehow other users are able to connect with your TL-WR841N.

If it was me I would write down (or print out) all the Internet-related settings from the "Network -> WAN" and "Network -> MAC Clone" menus and then reset the router to factory default settings (System Tools -> Factory Defaults) and then configure the router again from scratch. I would also think up a very new Wi-Fi password of which I am 100% sure that I am the only person to know it.