Well you have to set up a proper dns server. your router is obviously not performing that function. The only way I know how to do this is to access your router web interface (in other words, you open your web browser and type:http://192.168.0.1
This will open your routers interface and ask you for the username and password - I hope you remember what those are.
What you get after that depends on what router you are using. On my Netgear one I go to "Basic Settings" and in the section titled "Domain Name Server (DNS) Address" I click the "use these dns servers" radio button and in the primary and secondary dns servers boxes I enter
Primary DNS ... 220.127.116.11
Secondary DNS ... 18.104.22.168
That is because I am using 'OpenDNS'. There are many DNS servers so for example if you wanted to use the google servers you would enter:
Primary DNS ... 22.214.171.124
Secondary DNS ... 126.96.36.199
Which has the advantage of being easier to remember.
Alternatively you can use the ones provided by your isp if you know what they are.
In either case you have to click 'Apply' followed by 'Logout' in the router admin window.
There may be an easier way but I don't know it and that should work anyway.
Fujitsu Lifebook AH532. Intel i5 processor, 6Gb ram, Intel HD3000 graphics, Intel Audio/wifi. Realtek RTL8111/8168B Ethernet.Lubuntu 13.10,Ubuntu12.10 (Unity), Mint16 (Cinnamon), Manjaro (Xfce).