Check Gateway in README

README.md

@@ -1,2 +1,58 @@
 # PowerShell_Scripts
 Some useful PowerShell scripts
+
+## Check Gateway
+
+### How it works ?
+
+First, the script gets the gateway's IP address :
+
+`$LocalIP = (Get-WmiObject Win32_NetworkAdapterConfiguration | Where-Object {$_.IPEnabled}).DefaultIPGateway`
+
+Then, with the IP address, the script gets the MAC address of the gateway :
+
+`$MacAddress = ((Get-NetNeighbor -IPAddress $LocalIP).LinkLayerAddress)`
+
+And the public IP address with opendns.com :
+
+`$PublicIP = ((Resolve-DnsName -Name myip.opendns.com -Server resolver1.opendns.com).IPAddress)`
+
+Next, we got arrays containing the MAC addresses by manufacturer :
+
+```
+$MacFreebox = "F4-CA-E5"
+$MacLivebox = "00-37-B7"
+$MacApple = "BC-B8-63"
+$MacXiaomi = "E0-CC-F8"
+```
+
+The script cuts the MAC address of the gateway by 3 groups (bytes) :
+
+```
+$MacSplit = $MacAddress -split "-"
+$MacPrefix = $MacSplit[0] + "-" + $MacSplit[1] + "-" + $MacSplit[2]
+```
+
+Next, compares the MAC addresses with arrays :
+
+```
+if($MacFreebox -contains $MacPrefix) # Check for Freebox
+{$Router = "a Freebox"}
+elseif($MacLivebox -contains $MacPrefix) # Check for Livebox
+{$Router = "a Livebox"}
+elseif($MacApple -contains $MacPrefix) # Check for Apple Device
+{$Router = "an Apple device"}
+elseif($MacXiaomi -contains $MacPrefix) # Check for Xiaomi Device
+{$Router = "a Xiaomi device"}
+else # If router is unknown
+{$Router = "Unknown"}
+```
+
+And give the result of the comparison :
+
+```
+if ($Router -like 'Unknown') # In the case router is unknown
+{Write-Host "Router is unknown ($MacAddress). Maybe a randomized MAC address" ; exit 1}
+else
+{Write-Host "Gateway is $Router ($MacAddress). `nLocal IP is $LocalIP. `nPublic IP is $PublicIP." ; exit 0}
+```