Senior Network & Infrastructure for Multi-Site VPN, VoIP (Grandstream), and NAS Synchronization

​We are looking for an expert Network & Infrastructure Engineer to establish a secure, stable, and seamless Site-to-Site VPN connection between our main headquarters (already equipped with a production Grandstream PBX and Synology NAS) and two remote branches (one domestic and one international). The objective is to unify our internal communication system (extensions) and centralize file storage. ​The work will be 100% remote. Hardware is already on-site (Routers, Switches, IP Phones, Synology, and WD My Cloud NAS). Our local team will handle physical cabling and internet connectivity. ​Technical Tasks: ​Advanced Site-to-Site VPN: Establish encrypted VPN tunnels between branch routers and the main HQ. Crucial: You must implement VPN Obfuscation / Stealth VPN techniques and custom port configuration to bypass Deep Packet Inspection (DPI) and VoIP blocking in the international branch. ​Grandstream PBX Optimization & Expansion: Review our existing production PBX configuration, add new remote extensions, and ensure seamless internal transfers. Configure Inbound/Outbound routes so that remote employees can call out using the HQ’s main number. ​File Server & Synchronization: Configure the HQ Synology NAS as a network drive reachable over VPN. Set up GoodSync for automated, secure synchronization from branch WD My Cloud units to the HQ Synology server using internal Local IPs. ​QoS & VoIP Optimization: Configure advanced Firewall Rules and NAT Traversal. Implement Quality of Service (QoS) to prioritize VoIP traffic over data sync, ensuring crystal-clear voice quality even during large file transfers. ​Requirements & Deliverables: ​Proven Experience: Must have a track record of bypassing restrictive network environments and implementing Obfuscation successfully for VoIP services. ​Deep Expertise: Expert-level knowledge of MikroTik / Fortinet (Routing/VPN), Grandstream PBX (SIP/Extensions), and Synology NAS management. ​Acceptance Testing: The project is considered complete only after rigorous testing of internal/external calls and verified file synchronization across all branches without latency or packet loss. ​Technical Documentation: Provide a comprehensive PDF document including network diagrams, IP schemes, and credentials management. ​Post-Project Support: 30 days of technical support to resolve any stability issues during initial rollout. ​Security: Complete confidentiality is required; all default credentials must be replaced with strong, secure passwords upon completion.