Hello @Suryaprakash
It is possible to set a static ip on the WAN. Go to: Hardware - GX50 - Settings - IP configuration
![static ip.png static ip.png](https://community.meraki.com/t5/image/serverpage/image-id/32201i7DC37631CCEA7C02/image-size/medium?v=v2&px=400)
Leave VLAN blank and enter the IP for the GX50, the Gateway-IP and the DNS.
On the LAN side the GX50 always has a preset IP-address (x.x.x.1), not sure if you were talking about the GX50 LAN-IP or how to set Reserved IP addresses.
Infos can be found here Meraki Go - Local Network Addressing - Cisco Meraki
Cheers