4.1.e [i] 6in4, 6to4
6in4 is an Internet transition mechanism for migrating from Internet Protocol version 4 (IPv4) to IPv6. 6in4 uses tunneling to encapsulate IPv6 traffic over explicitly-configured IPv4 links as defined in RFC 4213 . The 6in4 traffic is sent over the IPv4 Internet inside IPv4 packets whose IP headers have the IP protocol number set to 41. This protocol number is specifically designated for IPv6 encapsulation. In 6in4, the IPv4 packet header is immediately followed by the IPv6 packet being carried. This means that the encapsulation overhead is simply the size of the IPv4 header of 20 bytes. With an Ethernet Maximum Transmission Unit (MTU) of 1500 bytes, one can thus send IPv6 packets of 1480 bytes without fragmentation. 6in4 tunneling is also referred to as proto-41 static because the endpoints are configured statically.
6to4 Tunneling is one of the IPv6 translation mechanism which encapsulates the IPv6 packets into IPv4 which allows remote IPv6 networks to communicate across the IPv4 infrastructure( core network or Internet). The main difference between the manual tunnels and automatic 6to4 tunnels is that the tunnel is not point-to-point but it is point-to-multipoint. In automatic 6to4 tunnels, the IPv4 infrastructure is treated as a virtual non -broadcast multi-access (NBMA) link routers are not configured as point-to-point. The IPv4 address embedded in the IPv6 address is used to find the other end of the automatic tunnel.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4655-4664). . Kindle Edition.
4.1.e [ii] ISATAP
ISATAP is an automatic overlay tunneling mechanism that uses the underlying IPv4 network as a NBMA link layer for IPv6. Overlay tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure (a core network). By using overlay tunnels, you can communicate with isolated IPv6 networks without upgrading the IPv4 infrastructure between them. Overlay tunnels can be configured between border devices or between a border device and a host; however, both tunnel endpoints must support both the IPv4 and IPv6 protocol stacks.
IPv6 supports the following types of overlay tunneling mechanisms:
● Generic routing encapsulation (GRE)
● Intra-site Automatic Tunnel Addressing Protocol (ISATAP)
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4668-4681). . Kindle Edition.
4.1.e [iii] 6RD
IPv6 Rapid Deployment (6rd) is a stateless tunneling mechanism which allows a Service Provider to rapidly deploy IPv6 in a lightweight and secure manner without requiring upgrades to existing IPv4 access network infrastructure. While there are a number of methods for carrying IPv6 over IPv4, 6rd has been particularly successful due to its stateless mode of operation which is lightweight and naturally scalable, resilient, and simple to provision.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4683-4686). . Kindle Edition.
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.