4.4.1. 6rd

6rd [RFC5969] specifies an automatic tunneling mechanism tailored to advance deployment of IPv6 to end users via a service provider's IPv4 network infrastructure. Key aspects include automatic IPv6 prefix delegation to sites, stateless operation, simple provisioning, and service that is equivalent to native IPv6 at the sites that are served by the mechanism. It is expected that such traffic is forwarded over the CE router's native IPv4 WAN interface and not encapsulated in another tunnel.

The CE router SHOULD support 6rd functionality. If 6rd is supported, it MUST be implemented according to [RFC5969]. The following CE Requirements also apply:

6rd requirements

6RD-1: The IPv6 CE router MUST support 6rd configuration via the 6rd DHCPv4 Option 212. If the CE router has obtained an IPv4 network address through some other means such as PPP, it SHOULD use the DHCPINFORM request message [RFC2131] to request the 6rd DHCPv4 Option. The IPv6 CE router MAY use other mechanisms to configure 6rd parameters. Such mechanisms are outside the scope of this document.

6RD-2: If the IPv6 CE router is capable of automated configuration of IPv4 through IPCP (i.e., over a PPP connection), it MUST support user-entered configuration of 6rd.

6RD-3: If the CE router supports configuration mechanisms other than the 6rd DHCPv4 Option 212 (user-entered, TR-069 [TR-069], etc.), the CE router MUST support 6rd in "hub and spoke" mode. 6rd in "hub and spoke" requires all IPv6 traffic to go to the 6rd Border Relay. In effect, this requirement removes the "direct connect to 6rd" route defined in Section 7.1.1 of [RFC5969].

6RD-4: A CE router MUST allow 6rd and native IPv6 WAN interfaces to be active alone as well as simultaneously in order to support coexistence of the two technologies during an incremental migration period such as a migration from 6rd to native IPv6.

6RD-5: Each packet sent on a 6rd or native WAN interface MUST be directed such that its source IP address is derived from the delegated prefix associated with the particular interface from which the packet is being sent (Section 4.3 of [RFC3704]).

6RD-6: The CE router MUST allow different as well as identical delegated prefixes to be configured via each (6rd or native) WAN interface.

6RD-7: In the event that forwarding rules produce a tie between 6rd and native IPv6, by default, the IPv6 CE router MUST prefer native IPv6.