Network Architecture & RoutingTUN Virtual Interface & RoutingDeep Technical Handbook (~15 mins)

TUN Virtual Interface & OSI Layer 3 Architecture: Deep Dive into Packet Interception vs System Proxy

Hardcore technical breakdown of TUN (Layer 3) network packet interception within OS networking stacks. Analyze the architectural differences between TUN, TAP, and L7 proxies, packet redirection mechanics, and Fake-IP translation lifecycles.

Key Takeaway (TL;DR): Application-level proxies (Layer 7) depend on software cooperation. TUN interfaces (Layer 3) intercept raw IP packets by registering virtual network adapters with high-priority split routes (0.0.0.0/1 and 128.0.0.0/1). Utilizing Longest Prefix Match routing principles, all OS outbound frames are ingested into user-space network stacks (gVisor/lwIP) while preserving physical gateway breakouts for provider tunnels.

1. Network Stack Comparison

TUN bypasses application-level proxy ignorance by operating at the IP packet layer, transparently capturing UDP, ICMP, and CLI utilities.

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