You will need to reconfigure your extender if you replace your existing router you reconfigure your extender either via WPS connection or using the web GUI.

WPS:

1) If your router supports WPS press WPS button on router www.mywifiext.net setup gateway for 5seconds until the WPS indicator light to initiate the connection. Netgear Extender Setup Learn the wifi extender setup using the WPS button.

2) Within 60 seconds press and hold the WPS button on extender for 5 seconds.

3) Wait for up to 5 minutes until WPS indicator stop blinking.

4) check if router link LED on extender is ON or OFF if link LED is ON your extender successfully connected to your router Wi-Fi network if link LED is OFF the extender failed to connect to router Wi-Fi network please repeat steps 1-3 to again

5) If your extender and router are dual-band devices repeat steps 1-4 configure the 5GHz network.Netgear Extender Login .

6) Move your extender to its preferred location which is ideally halfway between your router and area with poor Wi-Fi signal.

Web GUI:

1) Reset the extender by pressing and holding the reset button for 10 seconds using a paper clip or pin.

2) Once extender has complete its reboot connect your device to default SSID

3) Open your browser and you will automatically direct to extender setup page if not open enter in the address bar and press enter.

Go to official website ----> http://netgearextendersetup.us

4) Click new extender setup button.

5) Create a new account by filling out the required fields and click to continue.

6) The extender will search and display the Wi-Fi network available in the area.

7) Select Wi-Fi network of the router and click next button.

8) In the password field enter the www.mywifiext.netsetup network password for the network you selected and click next button. Router Login

9) Set network name and password of new extender network and click to next.

10) Connect your wireless device to a new extender Wi-Fi network using SSID and password created in the step above.

11) Click continue button to complete setup.

12) Click Next button to proceed to the registration process.

Original source :---> https://sites.google.com/site/ssmaartlinksyss/netgear-n300-wi-fi-range-extender-red-light