@Hometown420 

Hi,

In such a case the first thing to check is that the Google "what's my ip address" is the same IP address as the WAN IP address shown in the router's "Status" screen. If they are different, then it won't work that easily.

  @woozle 

Thank you for the response. My WAN IP Adress is not same as that of the Google "what's my ip address". What should i do to make it work. Any help would be appreciated.

  @Hometown420 

In case you have another router device connected between your broadband connection and your Archer C20, then log into that device and check if it gets the IP address you see with "what's my ip address".

But if your Archer C20 is connecting directly to your ISP, then your ISP is most likely routing you via their CG-NAT and assigns a private IPv4 address to your C20.

In that case you should contact your ISP and ask them if they can change that and assign a public IPv4 address instead. 
 

  @woozle 

I have connection between my main router broadband  and my Archer C20, but main router IP adress is not the same as seen with "what's my ip address". 

I tried with my main router IP address in Archer C20 too but again it shows 403 forbidden.

  @Hometown420 

Do you mean the "WAN" or "Internet" IP address shown on the status page of your main router is also not the same address as the "what's my ip address"?

Anyway, any IPv4 address that falls within the following segments of IP addresses is a private IP address and hence cannot be reached via the Internet.

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
100.64.0.0 - 100.127.255.255
 

In that case you can only contact your ISP and ask them to assign you a public IPv4 address.