Tag Archives: IPV6

6.3.e Describe IPv6 network address translation

6.3.e [i] NAT64

Network Address Translation IPv6 to IPv4, or NAT64, technology facilitates communication between IPv6-only and IPv4-only hosts and networks (whether in a transit, an access, or an edge network). This solution allows both enterprises and ISPs to accelerate IPv6 adoption while simultaneously handling IPv4 address depletion . The DNS64 and NAT64 functions are completely separated, which is essential to the superiority of NAT64 over NAT-PT.

All viable translation scenarios are supported by NAT64, and therefore NAT64 is becoming the most sought translation technology.

AFT using NAT64 technology can be achieved by either stateless or stateful means:

● Stateless NAT64 , defined in RFC 6145, is a translation mechanism for algorithmically mapping IPv6 addresses to IPv4 addresses, and IPv4 addresses to IPv6 addresses . Like NAT44, it does not maintain any bindings or session state while performing translation, and it supports both IPv6-initiated and IPv4-initiated communications.

● Stateful NAT64, defined in RFC 6146, is a stateful translation mechanism for translating IPv6 addresses to IPv4 addresses, and IPv4 addresses to IPv6 addresses. Like NAT44, it is called stateful because it creates or modifies bindings or session state while performing translation. It supports both IPv6-initiated and IPv4-initiated communications using static or manual mappings.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 6025-6028).  . Kindle Edition.



6.3.e Describe IPv6 network address translation

6.3.e [ii] NPTv6

NPTv6 is simply rewriting IPv6 prefixes. If your current IPv6 prefix is 2001: db8: cafe::/ 48 then using NPTv6 it would allow you to change it to 2001: db8: fea7::/ 48 – that is it. It is a one for one prefix rewrite – you can’t overload it, have mismatching prefix allocations sizes, re-write ports or anything else . Importantly, it doesn’t touch anything other than the prefix. Your network/ host portion remains intact with no changes.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 6032-6034).  . Kindle Edition.


6.3.c Implement and troubleshoot IPv4 and IPv6 DHCP

6.3.c [iv] SLAAC/DHCPv6 interaction

Stateless DHCPv6 is a combination of “stateless Address Autoconfiguration” and “Dynamic Host Configuration Protocol for IPv6” and is specified by RFC 3736. When using stateless-DHCPv6, a device will use Stateless Address Auto-Configuration (SLAAC) to assign one or more IPv6 addresses to an interface, while it utilizes DHCPv6 to receive “additional parameters ” which may not be available through SLAAC. For example, additional parameters could include information such as DNS or NTP server addresses, and are provided in a stateless manner by DHCPv6. Using stateless DHCPv6 means that the DHCPv6 server does not need to keep track of any state of assigned IPv6 addresses, and there is no need for state refreshment as result. On network media supporting a large number of hosts associated to a single DHCPv6 server, this could mean a significant reduction in DHCPv6 messages due to the reduced need for address state refreshments.

Stateless Address Autoconfiguration (SLAAC) is one of the most convenient methods to assign Internet addresses to IPv6 nodes. This method does not require any human intervention at all from an IPv6 user. If one wants to use IPv6 SLAAC on an IPv6 node , it is important that this IPv6 node is connected to a network with at least one IPv6 router connected. This router is configured by the network administrator and sends out Router Advertisement announcements onto the link. These announcements can allow the on-link connected IPv6 nodes to configure themselves with IPv6 address and routing parameters without further human intervention.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 5959-5966).  . Kindle Edition.



6.3.c Implement and troubleshoot IPv4 and IPv6 DHCP

6.3.c [vi] DHCPv6 prefix delegation

When DHCPv6 server has the Prefix Delegation feature enabled, it acts as a delegating router. The delegating router automates the process of assigning prefixes to the requesting router (that is, the DHCP client). Once the server has delegated prefixes to the client, the interface that is connected to the local area network (LAN) of the requesting router has an IPv6 address using the received prefix block. The requesting router then announces this address in the Router Advertisement messages. The client routers (that is, the routers in the local network) can use the autoconfig option to pull the global IP address from the advertised Router Advertisement messages by the DHCP client.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 5969-5972).  . Kindle Edition.


6.3.a Implement and troubleshoot first-hop redundancy protocols

6.3.a [ii] Redundancy using IPv6 RS/RA

IPv6 routing protocols ensure router-to-router resilience and failover. However, in situations in which the path between a host and the first-hop router fails, or the first-hop router itself fails, first hop redundancy protocols (FHRPs) ensure host-to-router resilience and failover.

The Gateway Load Balancing Protocol (GLBP) FHRP protects data traffic from a failed router or circuit, while allowing packet load sharing between a group of redundant routers . The Hot Standby Router Protocol (HSRP) protects data traffic in case of a gateway failure.

The Gateway Load Balancing Protocol feature provides automatic router backup for IPv6 hosts configured with a single default gateway on an IEEE 802.3 LAN. Multiple first hop routers on the LAN combine to offer a single virtual first-hop IPv6 router while sharing the IPv6 packet forwarding load. GLBP performs a similar function for the user as HSRP . HSRP allows multiple routers to participate in a virtual router group configured with a virtual IPv6 address. One member is elected to be the active router to forward packets sent to the virtual IPv6 address for the group. The other routers in the group are redundant until the active router fails. These standby routers have unused bandwidth that the protocol is not using. Although multiple virtual router groups can be configured for the same set of routers, the hosts must be configured for different default gateways, which results in an extra administrative burden. The advantage of GLBP is that it additionally provides load balancing over multiple routers (gateways) using a single virtual IPv6 address and multiple virtual MAC addresses. The forwarding load is shared among all routers in a GLBP group rather than being handled by a single router while the other routers stand idle. Each host is configured with the same virtual IPv6 address, and all routers in the virtual router group participate in forwarding packets.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 5841-5847).  . Kindle Edition.