ccnaWhat is Network Tunneling and how to configure Generic Routing Encapsulation (GRE) Tunnels?
Generic Routing Encapsulation (GRE) is a network tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network.
When do we use the GRE?
GRE is used when packets need to be sent from one network to another over the internet.
Generic Routing Encapsulation (GRE) has some disadvantages:-
GRE tunnel is an encapsulation protocol and does not perform any encryption.
When we create a GRE point-to-point tunnel without any encryption is extremely risky as sensitive data can easily be extracted from the tunnel and misused by others. ( That’s why we used IPSec to add an encryption layer and secure the GRE tunnel with the help of IPSec we get army-level encryption).
Classic GRE tunnel is a point-to-point, Manual tunnel, Not scalable, Static IP on all endpoints
GRE tunnel uses a ‘tunnel’ interface a logical interface configured on the router with an IP address where packets are encapsulated and decapsulated as they enter or exit the GRE tunnel.
All tunnel interfaces of participated routers must always be configured with an IP address that is not used anywhere else in the network.Each tunnel interface is assigned an IP address within the same network as other Tunnel interfaces. Before you configure you must adjust (MTU) maximum transfer unit and MSS maximum segment size.
Let’s see the configuration:-
