Which two headers are added to an existing packet by GRE? (Choose two.)
- 16-byte GRE header
- 16-byte IP header
- 4-byte CMD header
- 4-byte GRE header
- 20-byte IP header
Explanation: Generic Routing Encapsulation (GRE) creates a tunnel by adding two specific headers to the original packet. These include a 20-byte IP header, also known as the Delivery Header, which handles the transport of the packet across the network. Additionally, a 4-byte GRE header is added, which contains a protocol type field to identify the Layer 3 protocol being transported. Together, these headers result in a minimum of 24 bytes of additional overhead, effectively hiding the original packet headers from transit routers.
Related exam: Modules 17 – 20: Checkpoint Exam: Virtualization and Network Services Answers (CCNP ENCOR v9)
