If the laptop ethernet interface has 192.168.1.170 assigned, then that is the gateway IP for your Arduino. Normally, you would want 192.168.1.1 assigned to the laptop interface, but that IP should work.
edit: In the event you are not aware how all this ties together, I will explain simply.
The IP assignment sets the localnet IP range in conjunction with the subnet mask.
The subnet mask determines how big the localnet is. If the IP is 192.168.1.1, and the subnet mask is 255.255.255.0, then any IP between 192.168.1.0 and 192.168.1.255 is localnet. If the subnet mask is 255.255.0.0, then any IP between 192.168.0.0 and 192.168.255.255 is localnet.
The Arduino (or any device) will attempt to connect to any destination IP in that IP range directly. If the destination IP is outside that range, the Arduino (or any device) will send the request to the gateway IP. The gateway IP MUST BE in the localnet range or it will not be reachable.