I have a wifi modem/router. it has lan ports also. I want to connect my raspberry pi to the modem using Ethernet cable and I want to operate raspberry pi using putty in my laptop which is connected to the same modem using wifi. How to do it ? How do i get the ip of the raspberry pi so that i can use putty?
Method 1: Install a network scanner like Fing (free on iOS and Android), scan your WiFi and look for the hostname raspberrypi -- the ip next to it is the one you need.
Method 2: Depending on your router's (DNS) configuration, you may also be able to use the hostname in PuttY instead of the ip. The standard hostname is "raspberrypi" so you can simply try that or "raspberrypi.local".
P.S.: No explicit need to assign a static ip. Many routers keep giving the same ip to the same device as long as the DHCP address pool is not exhausted (e.g. by many wifi users). I'm running a similar setup and the Raspberry's ip hasn't changed in weeks even though it and the router were rebooted many times.