Though the WPS method of the Linksys RE6700 setup does not require any specific thing to execute. All this method requires is the WPS buttons on the existing router which must be compatible with the extender also. But, the other two processes that will also allow you to manage the network have some prerequisites. That you will need to execute the process completely. Which includes the extender itself with its login credentials that you can get from the manual setup guide. Also, you need to get the default web or IP address of the extender which will be required to access the setup window. 

More than that, your existing router with its SSID network name and password as well. Thereafter, collect an ethernet wire in case you want to make a wired connection for strong signals and better connectivity. The other requirement will be your device and access to the web browser and app store. So that, you will be on the setup window of the Linksys extender. Apart from that, make sure to check your device’s compatibility whether that is connectable to the extender or not. So, go through this list and collect the items as well to achieve a smoother process.