All addresses in x.x.x.0/25 are then available in the main office, and devices in the branch office will receive IPs starting (for example) from x.x.x.130/25. If all devices in the main office use static IP addressing, the existing DCHP pools and reservations can just be changed to provide IPs in range x.x.x.128/25. Using the current devices and IP ranges it means splitting the networks.
![configure router on a stick configure router on a stick](https://networkustad.com/wp-content/uploads/2019/08/Router-on-Stick-720x300.png)
![configure router on a stick configure router on a stick](https://www.interfacett.com/wp-content/uploads/2014/02/005-static-routing-in-IPv6-on-Cisco-Routers.png)
![configure router on a stick configure router on a stick](https://i.ytimg.com/vi/qHQLp7Bmhn0/maxresdefault.jpg)
Thought it might be beneficial to others to expand Maupin's comment to an actual answer.
CONFIGURE ROUTER ON A STICK PC
The only problem now is the pc on the Branch side is not getting the ip address. Gateway pc uses static ip address while Branch pc acquired their ip address through dhcp server which is the Gateway router. I don't know what i did wrong because i have configured the dhcp pool, subinterfaces and dhcp relay agent.