Edit 2026-02-18
Jan 20 Edit
Jan 16 Edit
Minor edit. A GRE (Generic Routing Encapsulation) tunnel is a network technology that allows one network to encapsulate packets and send them over another network, effectively creating a “tunnel” between two endpoints. GRE tunnels are often used to connect remote sites over the internet or to transport packets of one protocol inside another.
Edit 2. GRE encapsulates the original packet with a new GRE header and an outer IP header, allowing it to traverse networks that might not natively support the original protocol. Unlike VPNs, GRE does not provide encryption, so it is often combined with IPsec when secure transmission is needed.
Common use cases include connecting branch offices, supporting multicast traffic over unicast networks, and enabling IPv6 connectivity over IPv4 infrastructure. GRE tunnels are simple, flexible, and widely supported in routers and firewalls.
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