Automatic Configuration of IPv6 stateless addresses

As the next-generation Internet protocol, IPv6 solves many shortcomings and defects in the current IPv4 protocol, such as address scarcity and large route tables. One of the highlights is the automatic configuration of stateless addresses, which greatly reduces the workload of network workers.

1. IPv6 address format and address configuration method

A typical IPv6 host Unicast address consists of three parts: Global route prefix, subnet ID, and interface ID (64-bit ). The global routing prefix is used to identify an address range allocated to a site. A subnet ID is also called a subnet prefix. A subnet ID is associated with a link to identify a link in the site. The Interface ID is used to identify an interface on a link. It is unique on the link.

IPv6 address configuration can be divided into manual Address Configuration and automatic address configuration. The automatic address configuration method can be divided into stateless address automatic configuration and stateful address automatic configuration. In the automatic configuration mode of IPv6 stateless addresses, the network interface receives the global address prefix advertised by the router, and then obtains a globally Unicast address that can be clustered with the interface ID. In the mode of automatic configuration of stateful addresses, the Dynamic Host Configuration Protocol DHCP is mainly used). A dedicated DHCP server is required, the Network Interface obtains address configuration information from the DHCP server in Client/Server mode.

2. Interface ID generation

In the automatic configuration of IPv6 stateless addresses, the interface ID can usually be obtained through the EUI64 conversion algorithm. The Interface ID is converted from a 48-bit MAC address. EUI64 is a 64-bit extended Unique Identifier defined by IEEE. It is a combination of the IEEE-designated public 24-digit manufacturer identification and the 40-digit value specified by the manufacturer for the product. In an IPv6 address, the interface ID is 64-bit in length, which is obtained by converting the 48-bit Ethernet MAC address.

3. Obtain the global route prefix

A network node sends a router request RSRouterSolicitation to the router connected to it to obtain its global route prefix. The RS Message Type field value is 133, indicating that this is a router request message. The source address of the message is the local link address of the network node. Because this is a router request message, the destination address is FF02 :: 2 ).

After receiving the RS message from the network node, the router returns the RARouterAdvertisement message to the node. RA Message 3 is shown. The source address of the RA message is the IPv6 address of the router, and the destination address is the local link address of the network node. The message type field value is 134, indicating that this is a route notification message, the option field of the message provides the global route prefix 1 ::. After obtaining the global route prefix, the network node combines with the interface ID to form its Global IPv6 address. So far, the IPv6 Stateless Address automatic configuration process has ended.

4. Conclusion

The Interface ID obtained using the EUI64 conversion algorithm is fixed by the random device hardware and globally unique. This algorithm is easy to implement and is an important algorithm for Automatically Generating interface IDs. Currently, in Windows and Linux operating systems, EUI64 conversion algorithm is used to generate interface IDs for hosts. As an improvement to this algorithm, RFC3041 introduces a random address mechanism, which includes a set of random numbers instead of the Interface ID converted from the MAC address. The address has a certain life cycle. After the life cycle ends, the address will be automatically changed, which effectively solves the problem of Internet access activity tracking on the node.