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Techpaper Migration

LANCOM Glossary about IPv6


Here you can find a list with explanations of every term concerning the topic IPv6:

Dual stack

Dual stack means that an operating system can handle both IPv4 and IPv6 with the internal implementation of two separate protocol stacks (IPv4 and IPv6). The advantage of this approach is that one stack can be safely disabled without affecting the other. The idea is to turn off IPv4 once networks have been fully migrated. LANCOM highly recommends the usage of Dual Stack.


As with 6to4, the tunneling technique 6in4 packages IPv6 packets into IPv4 packets (protocol type 41). However, the tunnel endpoints have to be configured manually. The advantage of this solution is that a 6in4 tunnel is more stable and offers higher performance than a dynamic 6to4 tunnel. Disadvantages; configuration has to be carried out manually, a tunnel broker is necessary, and the dynamic IPv4 address of the customer must be communicated to the tunnel broker every time the address changes.


In a 6to4 tunnel, the IPv6 packets are packaged into IPv4 packets. The resulting IPv4 packet has the protocol type 41. No explicit tunnel setup is necessary because the packaged IPv6 packets are sent to the anycast address (6to4 relay). The selection of the 6to4 relay is determined by the routing protocol and depends on the geographical location of the user. A 6to4 address has the prefix 2002::/16 and the address structure 2002:::/48 This 6to4 address is calculated by a 6to4 router itself, based on its unique IPv4 address. Thus there is no explicit prefix allocation by a provider. A 6to4 tunnel is not considered to be a permanent solution but a pathway to smooth migration. Furthermore, 6to4 has some problems regarding accessibility. LANCOM does not recommend the usage of a 6to4 tunnel.

Duplicate Address Detection

Before a computer can use an IPv6 address on an interface, Duplicate Address Detection (DAD) checks to see whether the IPv6 address is already being used on the local network. This avoids address conflicts.

IPv6 adress prefix

An IPv6 address prefix consists of an IPv6 prefix and a prefix length. It identifies a block of address space or a network. An IPv6 prefix is the first part of the address in bits, which is always the same and thus denotes the network identifier. The prefix length indicates the number of bits that make up the network portion of the IPv6 address prefix. For example, the address prefix 2001:db8:0:0::/64 indicates that the prefix is 2001:db8:0:0 and the prefix length is 64 bits.

Link Local Address

A link-local address has the prefix fe80::/10 and is intended for communications within the segment of a local network (a link) only. It is mainly used for auto-configuration. Routers do not forward packets with this address.

Natives IPv6

Native IPv6 expresses a true IPv6 connectivity from a provider, for example over the PPP connection. This does not include connections that are established via a tunnel.


Network Address Translation is made obsolete by IPv6. All devices in the network receive a public global unicast address. In general, two configuration options are available on the central router with a corresponding IPv6 firewall. Either all computers can be made accessible from the outside, or a stateful firewall rule is used, which only allows connections to be established from the inside to outside, but not the other way around.

Neighbor Discovery Protocol

This protocol replaces IPv4's Address Resolution Protocol (ARP) to resolve IPv6 addresses into link-layer addresses. It is based on multicast and ICMPv6.

Stateful auto-configuration

Just as with IPv4 DHCP, DHCPv6 servers assign IPv6 addresses to the clients. A log is maintained documenting which client receives which address. This procedure requires significantly more effort than stateless auto-configuration.

Stateless auto-configuration

Stateless auto-configuration is a procedure by which a device generates an IPv6 address without a DHCPv6 server. The device generates an IPv6 address from the obtained network prefix and the interface identifier. The latter may be derived from the MAC address of the interface, for example. No records are kept about which client configured which address.


Teredo is a tunneling mechanism from Microsoft in which a tunnel is set up from clients behind a NAT router. IPv6 packets are packaged into IPv4 UDP packets. The remote end in the Internet is what is known as a Teredo relay. Since any Windows client can set up its own IPv6 tunnel and this tunnel then surpasses the firewall (including any ACLs and policies), this approach is regarded as critical for corporate networks. For corporate networks, a tunnel should be configured on the central router, which then protects all IPv6 traffic with a central IPv6 firewall. Teredo addresses have the prefix 2001:0000::/32.


An IPv6 tunnel transports IPv6 packets over an IPv4 network. Tunnels can be manually (fixed) or dynamically configured. There are numerous ways of packaging IPv6 packets into IPv4 packets.

Tunnel broker

A tunnel broker is a service provider offering IPv6 connectivity by using a tunnel mechanism. In most cases, tunneling protocols such as 6in4 are used in various forms. Examples of tunnel brokers are Hurricane Electric or SiXXS. After a mostly free registration, customers receive their own permanent prefix. The prefix length ranges from /64 (customers can set up one subnet) to /48 (65,536 subnets). The tunnel endpoint at the client end can be a router or even an application on a client PC. This client can establish a tunnel straight through a NAT router, for example by using 6in4 via UDP (NAT-Traversal).

Unique Local Address

Unique Local Addresses (ULA) with the prefix fc00::/10 are comparable with the private addresses in IPv4. These addresses can be used to set up networks that do not require connectivity to the Internet.