In this article you will find out the ways to change the gateway and/or the interface IP on the SMA 100 series appliance
Customers moving their devices from one network to another usually have this common question
One can change the Interface IP of the SMA device directly from the web UI if the old and the new IP address are behind the same gateway. In other words if the interface IP needs to be changed within the same network with a Single Gateway , it can be done from the web UI directly without losing access of the device except for a short interval. For example the X0 IP address currently is 192.168.200.10 and the Gateway is X0 which has the IP 192.168.200.1 , then you should be able to change the IP address to let's say 192.168.200.20 or 192.168.200.30 but on a condition that the new X0 IP address which is .20 or .30 has the same 192.168.200.1 as the gateway.
However if the Gateway needs to be changed along with the IP , the device has to be reset and reconfigured. From basic setup you can assign this device the new Gateway and IP. A back up of settings is highly recommended before resetting the device. This back up can then be "Partially" imported after the device is reset. The partial import can then make sure you do not lose your settings apart from the network configuration. Difference between partial and a full import is explained in the below article:
The reason you would have to reset the device for gateway change is that SonicWall does not provide the option to change the IP and the gateway at the same time on the SMA device(you would notice the gateway and the interface settings are on different areas on the UI). If you change the gateway (Network> Routes) you will lose access since the gateway will be changed but the interface IP will still be unchanged(which needs to be changed from Network > Interfaces on the web UI).And once the gateway is changed the device will not be accessible on the old interface IP. The same thing will happen if you change the interface IP first.
This is the recommended way to change the network Gateway.