Configuring a GRE Tunnel for IPv6 Traffic

CD

To configure a GRE tunnel between two remote sites to support the exchange of IPv6 traffic over an IPv4 network, you need to perform the following steps:

1. Enable the GRE interface for IPv4 operations: This is required because the tunnel will be encapsulating IPv6 traffic within IPv4 packets. Therefore, the GRE interface must be enabled for IPv4 operations to ensure that the packets are properly encapsulated and transmitted across the IPv4 network.

2. Add a static route for the remote IPv6 destination subnet with the remote tunnel endpoint as the next hop at each site: This step is necessary to ensure that IPv6 traffic is routed through the GRE tunnel. A static route must be added at each site that specifies the remote IPv6 destination subnet and the remote tunnel endpoint as the next hop.

   For example, suppose that Site A has an IPv6 subnet of 2001:db8:1::/64 and Site B has an IPv6 subnet of 2001:db8:2::/64. In this case, a static route must be added at Site A that specifies the destination subnet as 2001:db8:2::/64 and the next hop as the IP address of the remote tunnel endpoint at Site B. Similarly, a static route must be added at Site B that specifies the destination subnet as 2001:db8:1::/64 and the next hop as the IP address of the remote tunnel endpoint at Site A.

3. Increase the MTU to no less than 2500: This step is necessary because IPv6 packets are typically larger than IPv4 packets. Therefore, to ensure that IPv6 traffic can be properly transmitted across the GRE tunnel, the MTU must be increased to a value that can accommodate the larger packet size.

   A value of no less than 2500 is recommended to provide sufficient headroom for encapsulation overhead and to ensure that fragmentation is avoided.

4. Enable the GRE interface for IPv6 operations: This step is required to ensure that the GRE interface can properly handle IPv6 traffic. The GRE interface must be enabled for IPv6 operations to allow the encapsulated IPv6 traffic to be properly processed and delivered to its destination.

In summary, the correct configuration elements required to configure a GRE tunnel between two remote sites to support the exchange of IPv6 traffic over an IPv4 network are:

• Enable the GRE interface for IPv4 operations
• Add a static route for the remote IPv6 destination subnet with the remote tunnel endpoint as the next hop at each site
• Increase the MTU to no less than 2500
• Enable the GRE interface for IPv6 operations (optional, but recommended)