1.4 Explain common networking ports, protocols, services, and traffic types
IP Protocol Types
📘CompTIA Network+ (N10-009)
1. What is GRE?
GRE is a tunneling protocol.
- A tunneling protocol allows one network protocol to be encapsulated (wrapped) inside another protocol to be sent over a network.
- GRE is used to create a virtual point-to-point connection between two networks, even if they are separated by other networks like the internet.
Think of GRE as a “wrapper” that lets one type of network traffic travel across another type of network safely.
2. Key Features of GRE
- Encapsulation: GRE takes packets (data units) from one protocol and wraps them inside IP packets for transport.
- Protocol Agnostic: GRE can encapsulate many types of network layer protocols, not just IP. This means it can carry things like IPv4, IPv6, or even non-IP protocols.
- Virtual Tunnels: GRE allows you to create point-to-point tunnels between devices like routers.
- Works over IP networks: The encapsulated traffic travels inside normal IP packets over the internet or private networks.
3. How GRE Works
- A router or device wants to send a packet to a remote network.
- GRE encapsulates the original packet inside a new IP packet (adds a GRE header).
- The new packet is sent over the internet or a private IP network to the destination router.
- The destination router removes the GRE header and forwards the original packet to its intended destination.
Diagram Representation (Simplified):
Original Packet -> GRE Header Added -> IP Packet -> Sent over Network -> GRE Header Removed -> Original Packet Delivered
4. GRE in IT Environments
- VPNs: GRE is often used in VPNs (Virtual Private Networks) to carry traffic between different sites. For example, if a company has two offices, GRE can create a secure tunnel between them.
- Carrying Non-IP Traffic: GRE can transport protocols that normally can’t travel over an IP network.
- Combining with IPsec: GRE can be used alongside IPsec for secure VPNs. GRE handles the tunneling, while IPsec handles encryption and authentication.
5. Pros and Cons of GRE
Pros:
- Works with multiple protocols, not just IP.
- Simple and widely supported.
- Can create point-to-point connections over any IP network.
Cons:
- GRE itself does not encrypt traffic, so it’s not secure by default. Encryption must be added separately (e.g., IPsec).
- Adds extra overhead because of the additional GRE headers, which can slightly reduce network performance.
6. GRE Header Basics
- GRE adds a header to each packet to help the receiving device understand how to process it.
- The header includes information like the protocol type being encapsulated.
- GRE uses Protocol Number 47 in the IP header to identify GRE traffic.
Key point for exam: If a question asks about GRE protocol number, the answer is 47.
7. GRE Exam Tip
For the Network+ exam, you should know:
- GRE is a tunneling protocol.
- GRE encapsulates packets inside IP to send them across networks.
- GRE can carry multiple protocols, not just IP.
- GRE itself is not encrypted (use with IPsec if encryption is needed).
- GRE uses protocol number 47 in the IP header.
✅ Summary in Simple Terms
- GRE = “packet wrapper” for creating tunnels across networks.
- Lets different protocols travel over IP networks.
- Commonly used in site-to-site VPNs.
- Not secure on its own (add encryption if needed).
- Recognized by IP protocol number 47.
