Thanks for ur reply .
(well I use WPA2 )
And I read ur links ty
~Also I wasnât talking about ARP spoofing no~
Lets just imagine a scenario where for âexampleâ the persons( hackers ) Spoofing my MAC address broke in my home and got access to my Router lol or they used sniffing hacking tools and discovered my MAC address âŚand that they are near me like a neighbour ! so,very close.
And yes im aware of this that some people do not consider this very problematic but strangely others do so its a bit controversial subject? 
That site explains it very well 
quote
:"Another security technique some people use is MAC address filtering. Each computer and device contains a unique MAC address, thus the network administrator can create a black and white list of addresses he or she wants to block or to allow onto the network. This can be used with or without wireless encryption or the hidden network technique. If a hacker suspects a target network is using MAC address filtering, sheâd just have to bring up a wireless surveying or analyzer program on her laptop " ..." She would simply check out the list of stations or monitor the raw data packets to find a âgoodâ MAC address that he could use. Once a hacker has a MAC address she can emulate, in Windows, she would just bring up the network adapterâs properties dialog and type in the address, . In this way, the hacker wonât be stopped by the MAC address filter." from " 7 Things Hackers Hope You Donât Know" ( eSecurityPlanet )
And what I was referring to this website explains it very clearly it says :
"Each networked device or network interface is assigned a unique Media Access Control address (MAC). MAC address spoofing (or MAC spoofing) is a technique of "faking" this address. Although some legitimate cases exist for doing this, it is also used to circumvent existing security mechanisms, impersonate legitimate devices (end stations or even routers) or to hide an attacker. To combat this technique and protect your network, both detection and protection is required ."
quote from article "Detecting and Preventing MAC Spoofing "(from website Infoexpress)
So yes but when u said " In GlassWire it should show up as a duplicate MAC address in the Network tab"
How to know if it not spoofed or cloned router ?
So iâm just wondering if Glasswire can detect this or not âŚor if not it would be great if it could ?!