GRE Generic routing encapsulation

Tunneling protocol used to encsuplte a wide varity of network layer protocols inside a virtual point to point network.

universal translator when connecign similar network topologies over a network.

Versitility and intergration

GRE (Generic Routing Encapsulation)

Definition

• A tunneling protocol that encapsulates a wide variety of Layer 3 protocols inside virtual point-to-point links.
• Think of it as a universal translator for networks → allows different or similar network topologies to interconnect over an IP network.

---

Key Features

• Encapsulation only → GRE does not provide encryption or confidentiality (must pair with IPsec if security is required).
• Supports multicast, broadcast, and non-IP protocols across IP networks (unlike many VPNs).
• Provides a virtual point-to-point connection between routers.
• Commonly used for:
  • Site-to-site tunnels
  • VPNs needing multicast (e.g., routing protocol traffic)
  • Interconnecting remote offices with different topologies

---

Advantages

• Versatility: Can encapsulate many protocols.
• Integration: Works with existing IP infrastructure.
• Flexibility: Often layered with IPsec for secure, encrypted tunnels.

---

✅ Must-Know for Exam

• GRE = encapsulation, not encryption.
• Used as a universal translator to tunnel different network protocols.
• Often paired with IPsec → “GRE over IPsec” for secure site-to-site VPNs.
• Supports multicast & broadcast (important for routing protocols).

---

⚡ Flashcards

• Q: What does GRE provide?

  A: Encapsulation of many protocols, point-to-point tunneling.

• Q: Does GRE encrypt traffic?

  A: No (needs IPsec for security).

• Q: Why is GRE often used with routing protocols?

  A: Because it supports multicast/broadcast.