I built their IT Network from beginning.
1- Created a local network to link computers and resources together
2- I was Created Hardware Firewall PFSense (Handmade (I added it Squid Proxy for Free Anti-Virus & Management).
3- I linked between the branches by a protocol IPsec.
4- I did configurations & Management for Grandstream (UCM6204) it is VIOP System & MikroTik RB1100x4 Router