GRE Tunnel
GRE (Generic Routing Encapsulation) Tunnel is a tunneling protocol that encapsulates a wide variety of network layer protocols inside virtual point-to-point links over an IP network. It creates a secure, private connection between two endpoints by wrapping the original packets in a GRE header and an outer IP header, enabling the transport of non-IP protocols or private IP addresses across public networks. GRE is commonly used in VPNs, network virtualization, and connecting disparate networks over the internet.
Developers should learn GRE Tunnel when building secure network connections between geographically separated data centers, implementing site-to-site VPNs, or transporting multicast or legacy protocols over IP networks. It's particularly useful in cloud environments, hybrid cloud setups, and software-defined networking (SDN) where encapsulation is needed to extend private networks across public infrastructure, such as with AWS VPC peering or Azure VPN Gateway.