GCIA Fundamentals of Traffic Analysis Practice Test 2026 - Free Traffic Analysis Practice Questions and Study Guide

Teredo traverses NATs by using UDP as the transport protocol. It encapsulates IPv6 in UDP over IPv4 and sends those datagrams through UDP to Teredo servers and relays, which allows NAT devices to handle the traffic more predictably and supports hole punching and keep-alive mappings. UDP is a connectionless, firewall-NAT friendly protocol, which makes it well suited for crossing NATs without the overhead and statefulness of TCP. In contrast, TCP’s connection-oriented nature and reliability mechanisms complicate NAT traversal, ICMP is often blocked or not reliable for tunneling, and GRE is a separate tunneling method not used by Teredo for NAT traversal. So the predominant transport used by Teredo is UDP.