GRE tunnels connect discontinuous sub-networks.

GRE tunnels provide workarounds for networks with limited hops.

GRE tunnels encase multiple protocols (IPX) over a single-protocol backbone.

Advantages of GRE tunnels include the following: In contrast to IP-to-IP tunneling, GRE tunneling can transport multicast and IPv6 traffic between networks. GRE tunnel endpoints send payloads through GRE tunnels by routing encapsulated packets through intervening IP networks. GRE works by encapsulating a payload - that is, an inner packet that needs to be delivered to a destination network - inside an outer IP packet. GRE is used when IP packets need to be sent from one network to another, without being parsed or treated like IP packets by any intervening routers. Generic Routing Encapsulation (GRE), defined by RFC 2784, is a simple IP packet encapsulation protocol. Generic Routing Encapsulation (GRE) is a protocol that encapsulates packets in order to route other protocols over IP networks.

Before that lets explore the the both types of protocols in brief.

In this blog, we will discuss GRE vs IPSec in detail.

Cisco 5505 asa with ipsec tunnel