Analisis Keamanan VPN Site-to-Site Berbasis IPSec terhadap Serangan Sniffing pada Jaringan Multi-Gedung

Inter-building data communication over public networks is highly susceptible to sniffing attacks, particularly when unencrypted protocols such as File Transfer Protocol (FTP) are used, allowing sensitive information to be intercepted by unauthorized parties. This study analyzes the effectiveness of an IPSec-based Site-to-Site Virtual Private Network (VPN) in securing inter-building communication at Universitas Bina Darma against sniffing attacks. An experimental method compared network conditions before and after VPN implementation on a topology of three MikroTik routers, three switches, and three client devices. Evaluation included connectivity testing, FTP login and file transfer simulations, and packet analysis using Wireshark with port mirroring. Results show the IPSec tunnel was successfully established using AES-256-CBC encryption and SHA-256 authentication, with all connectivity tests achieving 0% packet loss, indicating no impact on network performance. Before deployment, all FTP packets, including credentials and file contents, were captured and read in plaintext. After activation, FTP packets were no longer detected, and all traffic was encapsulated into 37 ESP packets in ciphertext form, unreadable to attackers. These results demonstrate that IPSec-based Site-to-Site VPN effectively enhances confidentiality without compromising network connectivity, providing a practical contribution to educational institutions and complementing previous research.