4.1.e Describe IPv6 tunneling techniques

4.1.e [iv] 6PE/6VPE

The 6PE feature is particularly applicable to Service Providers who already run an MPLS network or plan to do it. One of the Cisco 6PE advantages is that there is no need to upgrade the hardware , software or configuration of the core network. Thus it eliminates the impact on the operations and the revenues generated by the existing IPv4 traffic. MPLS has been chosen by many Service Providers as a vehicle to deliver services to customers. MPLS as a multi-service infrastructure technology is able to provide layer 3 VPN, QoS, traffic engineering, fast re-routing and integration of ATM and IP switching. It is in a very natural manner that MPLS is put to contribution to ease IPv6 introduction in existing production networks.

MPLS de-coupling of the control plane and data plane provide an interesting alternative to the integration and co-existence of IPv4, IPv6 and ATM over a single infrastructure, thus fulfilling environments such as 3G networks where UMTS Release 5 needs in terms of transport: Cisco 6PE for IPv6 traffic, ATM over MPLS and regular IPv4 switching with its VPN, traffic engineering and QoS extensions. From an operational standpoint, new CEs introduction is straightforward and painless as it leverages the Layer 3 VPN scalability. Using tunnels on the CE routers is the simplest way to deploy IPv6 over MPLS networks. It has no impact on the operation or infrastructure of MPLS, and requires no changes to either the P routers (they don’t have to be IPv6 aware) in the core or the PE routers connected to the customers. 6VPE is a technology that allows IPv6 VPN customers to communicate with each other over an IPv4 MPLS Provider without any tunnel setup, by having the customer VPNv6 prefixes using a v4-mapped IPv6 address as next-hop inside the provider’s network and using IPv4 LSPs between the 6VPEs. In 6VPE, labels must be exchanged between the 6VPEs for their VPNv6 prefixes, which means that the VPNv6 address-family must be activated on the IPv4 iBGP session between the 6VPEs.

By default, the mpls ip propagate-ttl command is enabled and the IP TTL value is copied to the MPLS TTL field during label imposition. To disable TTL propagation for all packets, use the no mpls ip propagate-ttl command. To disable TTL propagation for only forwarded packets, use the no mpls ip propagate forwarded command . Disabling TTL propagation of forwarded packets allows the structure of the MPLS network to be hidden from customers, but not the provider.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4705-4710).  . Kindle Edition.