In this section, we'll see how to make IPv6-only hosts communicate with other IPv6-only hosts through IPv4-only devices. There are several methods for doing this; we'll discuss IPV6 over IPv4 tunneling using Generic Routing Encapsulation (GRE).

The GRE method encapsulates IPv6 packets within IPv4 packets and transports them over the IPv4 network. The receiving device decapsulates the packet and sends only the IPv6 information to the host. For this exercise, we'll use the following topology:

For routing, we will configure EIGRP on IPv4 interfaces for the three routers and static routing on R2 and R3. We will begin by configuring R1, which is the IPv4-only router.

R1(config)#int fa0/0
R1(config-if)#no shutdown
R1(config-if)#ip add 10.0.0.1 255.255.255.0
R1(config)#int fa0/1
R1(config-if)#no shutdown
R1(config-if)#ip add 10.2.0.1 255.255.255.0
R1(config-)#router eigrp 1
R1(config-router)#network 10.0.0.0

Now on the router R2, we will configure IPv4 and IPv6 addresses...