Detailed explanation of IPv6 address configuration and packet format: Network engineers must be familiar with IPv6. IPv6 is the abbreviation of “Internet Protocol Version 6” in English, which is the 6th edition of the Internet Protocol. It is the next generation IP protocol designed by the Internet Engineering Task Force to replace IPv4. Its number of addresses claims to be able to program an address for every grain of sand in the world. So what exactly is an IPv6 address? Why is it so powerful? Next, SPOTO will introduce the IPv6 address configuration and packet format in detail.
Classification of IPv6 addresses An IPv6 address is 128 bits long, which is four times the length of an IPv4 address. Therefore, the IPv4 dotted decimal format is no longer applicable, and it is expressed in hexadecimal, usually written in groups of 8. IPv6 addresses can be divided into three types: unicast addresses, multicast addresses, and anycast addresses. And what’s the difference between them? Let’s explain further.
The unicast address is used to uniquely identify an interface, similar to the unicast address of IPv4. Data packets sent to the unicast address will be transmitted to the interface identified by this address. In the IPv6 unicast address
Detailed introduction to IPv6 address configuration and packet format: IPv6 must be familiar to network engineers. IPv6 is the abbreviation of “Internet Protocol Version 6” in English, which is also known as the 6th version of the Internet Protocol. IPv6 is the next-generation IP protocol designed by the Internet Engineering Task Force to replace IPv4. It is said that the number of addresses it claims can be programmed with an address for every grain of sand in the world. So what exactly is an IPv6 address? Why is it so powerful? Now, let us introduce the IPv6 address configuration and packet format in detail.
What are the classifications of IPv6 addresses? An IPv6 address is 128 bits long, which is four times the length of an IPv4 address. Therefore, the IPv4 dotted decimal format is no longer suitable for IPv6, and must be represented in hexadecimal, usually written in groups of 8. IPv6 addresses can be divided into three types, namely unicast addresses, multicast addresses, and anycast addresses. What is the difference between these three?
The unicast address is used to uniquely identify an interface, similar to the unicast address of IPv4. Data packets sent to the unicast address will be sent to the interface identified by this address.In the IPv6 unicast address, it also includes the global unicast addresses, link-local addresses, loopback addresses, and unspecified addresses, etc.;
Multicast addresses are used to identify a group of interfaces, similar to IPv4 multicast addresses. Data packets sent to the multicast address will be transmitted all interfaces identified by this address; Anycast addresses are also used to identify a group of interfaces, but unlike multicast addresses, data packets sent to an anycast address will be measured according to the routing protocol used and sent to in the set of interfaces identified by this address, the interface closest to the source node.
It is worth noting that there is no broadcast address in IPv6, and the function of broadcast address is realized by multicast address.
IPv6 address configuration. Next, SPOTO will introduce the global unicast address configuration method to you. There are four main types, which are formed using IEEE EUI-64 format, manual configuration, quoting prefix to generate IPv6 address, and stateless automatic configuration.
Formed in IEEE EUI-64 format, at present, IPv6 unicast addresses basically require the interface identifier to be 64 bits. When the EUI-64 address is generated, it is derived from the MAC address of the interface, and the MAC address is 48 bits. Therefore, it needs to be in the 24th bit from the high order of the MAC address. After that, insert the hexadecimal number FFFE. In order to make the scope of the interface identifier consistent with the original MAC address, the seventh bit from the high-order bit must be inverted, and the finally obtained group of numbers is used as the interface identifier in EUI-64 format.
Manual configuration, for manual configuration, users can manually configure IPv6 prefixes, interface identifiers, and masks based on actual address planning.
Before generating an IPv6 address by referencing a prefix, you need to manually create a static IPv6 prefix with the ipv6 prefix command or obtain an IPv6 prefix dynamically by a DHCPv6 client.
Stateless auto-configuration: Stateless auto-configuration, the SWA switch interface is configured to cancel the suppression of publishing RA messages, the SWB switch interface is configured to automatically configure an IPv6 address to simulate a terminal, and view the interface address of the SWB device, and the SWB the IPv6 interface prefix of the SWA and generates an IPv6 address based on its own interface MAC.
Message format of IPv6 address: The overall structure of an IPv6 message is divided into three parts: IPv6 header, extension header and upper layer protocol data. The IPv6 header is a mandatory header with a fixed length of 40B and contains the basic information of the message; the extension header is an optional header, and there may be 0, 1 or more. The IPv6 protocol realizes various richness through extension headers; the upper-layer protocol data is the upper-layer data carried by the IPv6 packet, which may be ICMPv6 packets, TCP packets, UDP packets, or other possible packets.