GRE Tunnels

CD

GRE (Generic Routing Encapsulation) is a protocol used to encapsulate various protocols and send them over an IP network. It is often used to create tunnels between two endpoints, allowing communication between two networks as if they were directly connected.

The two statements that are true regarding GRE tunnels are:

C. GRE tunnels can be used to send non-routable packets over a public IP network. This statement is true. GRE tunnels can encapsulate any protocol, including non-routable protocols such as NetBIOS or IPX, and send them over a public IP network. By doing so, it enables communication between devices that are not directly reachable on the public IP network. GRE can also be used to encapsulate multicast traffic, which is not supported by some public IP networks.

D. GRE tunnels can be used as backup links. This statement is also true. GRE tunnels can be configured as backup links to provide redundancy in case of primary link failure. By configuring a GRE tunnel as a backup link, traffic will be routed through the tunnel only if the primary link fails. In addition, GRE tunnels can be used with routing protocols such as OSPF or BGP to provide load balancing and failover between multiple links.

A. GRE can be used to tunnel IP packets only. This statement is false. GRE can encapsulate any protocol, not just IP packets. It can be used to encapsulate non-IP protocols such as IPX or NetBIOS, allowing them to be transmitted over an IP network.

B. A GRE tunnel can be applied only at the physical interface level. This statement is false. A GRE tunnel is a logical interface and can be applied at any level of the networking stack, not just at the physical interface level. GRE tunnels can be configured on top of other protocols, such as IPsec or MPLS, to provide additional security or traffic engineering capabilities.