An example network device receives an encapsulated network packet via a network tunnel; extracts IPv6 header information from the encapsulated network packet; extracts IPv4 header information from the encapsulated network packet; determines that the encapsulated network packet is a spoofed network packet based on the IPv6 header information and the IPv4 header information; and in response to detecting the spoofed network packet, transmits a message to a Tunnel Entry Point (TEP) device, the message including data representing the IPv6 header information and IPv4 header information. A tunnel entry point (TEP) device may receive the message and use the message to detect spoofed IPv6 traffic, e.g., when an IPv6 header and an IPv4 header of an encapsulated packet matches the IPv6 header and the IPv4 header specified in the message. In this manner, the TEP device may block, rate limit, or redirect spoofed network traffic.