6RD (IPv6 Rapid Deployment) is a stateless automatic tunneling mechanism that connects two IPv6 islands via an IPv4 island. 6RD is very scalable and, as the name implies, can be deployed quickly.

A popular use case is for 6RD comes from a Service Provider in France called Free. In 2007, Free only offered its customers IPv4 access until a petition was signed by 20,000 customers to request that Free offer them IPv6 connectivity. In less than five weeks, Free provided IPv6 Internet access to 1.5 million residential customers. Rapid Deployment, indeed!

  • From the Service Provider’s perspective, IPv6 connectivity can quickly be offered to many customers while slowing the migration of the SP’s internal network from IPv4 to IPv6.
  • From the customer’s perspective (and the IPv6 island on the other end of the tunnel), 6rd works the same as native IPv6.

6RD was built on, and replaces, a tunneling technology called 6to4. 6to4 was never widely adopted because it has some significant flaws. For example, to use 6to4 all SP’s are required to use the well-known prefix of 2002::/16. An SP could receive traffic intended for a different SP!

6RD offers enhancements including:

  • It uses the service provider’s IPv6 prefix. The result is that operational domain is limited to the SP’s network and the SP has direct control over the traffic.
  • The attack surface is reduced as the SP will only have 6RD traffic from its own customers.

How it Works

Let’s take a look at an example where an SP with an IPv4 infrastructure wants to offer IPv6 connectivity customers. This topology has two BR routers that connect to different points on the IPv6 Internet. Since 6RD is stateless, return packets can come through either BR. All tunnel interfaces are multi-point.

Let’s define components:

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