Configuring a GRE tunnel involves multiple steps. The tunnel's physical interface must be configured first. Next, the supported protocols and the tunnel's IP address must be configured. Once these configurations are completed, these configurations must be applied to the tunnel.
The tunnel's main configurations are applied to a VE interface. The configurations of this VE interface are then applied to the tunnel as its Router Interface. The VE interface sets the supported protocols and the IP address(s) of the tunnel.
The following is the steps to perform to create and operate a tunnel that supports both IPv4 and IPv6 traffic through the same IPv4 GRE tunnel.
Create the Loopback Interface. This is used as the source interface for the tunnel. You can also use an IP address, VE, or an Interface as the source.
Create the Router Interface. This configures the most important parameters for the tunnel. Configurations includes the supported protocols and the IP addresses for the underlying tunnel endpoints.
Create the GRE tunnel and apply the above configurations to it.