IPv6 NAT-PT

In the recent posts, we discussed how we can transport IPv6 traffic over IPv4 backbone using the tunneling techniques. 

These techniques will not work if we have one part of network which can only run IPv4 and the other part can only run IPv6. Since IPv4 and IPv6 are not compatible with each other, we have to use some sort of translation mechanism. The way we can achieve this is through NAT-PT (NAT protocol translation).

Let's look at the below topology and see how NAT-PT can be implemented.

We have three routers R1, R2 and R3. We are running RIPng and RIPv2 between R1-R2 and R2-R3 respectively. R1 is only aware about IPv6 addresses, similarly R3 is only aware about IPv4 addresses.

Our goal is to establish reachability between the IPv6 loopback (2001:1111::1/128) of R1 to IPv4 loopback (3.3.3.3/32) of R3.

Site To Site VPN between Cisco Routers with Duplicate LAN IP

In the real world If there is a requirement to setup a site to site VPN connection between two different companies, there may be a specific scenario where both the companies are using the same LAN subnets. In this case, we cannot define the ACL with interesting traffic as the source and the destination subnets will be the same!

We will use the existing topology to illustrate the situation. As one can see, both R1 and R2 has a lookpback0 interface with IP 1.1.1.1/24 which represents the LAN subnet. We need to setup a site to site VPN between these two routers.

We will skip the usual steps to configure the ISAKMP & IPSEC parameters as we have covered those in previous posts. Our focus will be on how we can define the interesting traffic.