This is the 20th day of my participation in the August More Text Challenge

Following the book, this paper introduces IPV6 anycast and multicast address types in detail, and summarizes the differences and connections between IPV6 and V4 addresses

Anycast Anycast address

  • The address comes from the unicast address space, and the syntax is the same as unicast. Therefore, when assigning anycast address to a node, the type of anycast must be explicitly set to Anycast.

  • When a packet is sent using an Anycast address, the packet is sent to the “nearest” interface, which is calculated according to different routing protocols. This “nearest” interface may be a Hop or a distance.

  • One kind of anycast address format is specially defined, that is, router anycast address, as shown in the following figure.

  • The subnet prefix identifies a specific link link. The prefix is the same as the Unicast address of other interfaces on the link. Packets destined for the anycast address of the router are sent to the router with the shortest path in the subnet. All routers in the subnet must support the Anycast address of the router.

Multicast Multicast address (Multicast)

  • Multicast addresses are used to assign a set of interfaces, usually on different nodes, and data is sent to all interfaces that own the address. An interface can have multiple multicast addresses, and a node can listen to multiple multicast addresses at the same time.

  • Address format, the first 8 bits fixed 1, namely ff00::/8,

  • Flag fields of 0 | R | | T P:

    • The first bit is the reserved bit, which must be 0;
    • The second R indicates the multicast address of the sink, as described in RFC3956
    • The third bit P is in the Unicast prefix-based multicast address format. For details, see RFC3306.
    • The fourth bit T refers to the life cycle. 0 indicates that the address is a permanently valid multicast address assigned by IANA, and 1 indicates that the address is a temporary multicast address.

  • Scope indicates the routing range of the address: Local interfaces include interface-local (used for loopback multicast), link-local, Local management (configured by an administrator), site-local, and organization-local (used for multiple sites multicast).

  • Predefined multicast addresses:
    • FF01::1(interface-local Multicast addresses of all nodes in the Local Interface range)
    • FF01::2(interface-local Indicates the multicast addresses of all routers in the Local Interface range)
    • FF02::1(link-local Multicast address of all nodes in the local link-range)
    • FF02::2(link-local All router multicast addresses)
    • FF05::2(site-local all routers multicast address)
    • FF02:0:0:0:0:1:FFXX:XXXX. The last six digits of the unicast or anycast number of the Node are the last six hexadecimal digits. For example, 2000::01:800A:200E:8C6C, then its request node address is FF02::1:FF0E:8C6C, the last six bits are the same;

An address that must be configured for a node

  1. For host hosts, the following addresses must be configured:

    • Each interface has a link-local address.
    • Any additional Unicast and Anycast unicast addresses
    • Loopback address;
    • All predefined multicast addresses of nodes, including link-local, site-local, and interface-local
    • Solicted-node Address for each Unicast and anycast
    • Addresses of all other multicast groups to which the node belongs

  2. For routers, the following addresses must be configured:

    • Subnet-router Anycast addresses must be configured for each interface configured with routes

    • All other anycast addresses

    • All predefined router multicast addresses

Comparison between IPV6 and V4

Just from the address dimension, let’s look at the differences and connections between the two protocols

project V4 V6
object By node or device A node can have multiple different types of addresses assigned by interface
capacity 32bits 128bits
format xxxx.xxxx.xxxx.xxxx Use colon split, full format, short format
CIDR Yes, use /n to identify binary network number bits The prefix prefix, /N, stands for the binary network number number
The broadcast address support If no, use the multicast address instead
The multicast address support The scope and flag fields are added, and multiple multicast addresses are preset. The interface is added by default
anycast no Supports, and unicast common address, and specifies anycast address format for routes
The private network address Supported. Separate network segments Local unique address: specifies a network segment. The address must be unique across the network
The loopback address support support
compatibility Supports IPV6 communication through NAT and BGP Set a dedicated network segment to map IPV4 addresses

The above! If there is any inaccuracy or error, please leave a comment. I will correct it immediately. Thank you!





Summary is not easy, please do not reprint without permission, otherwise don’t blame old uncle you are welcome

Welcome technical friends to communicate with me, wechat 1296386616

References:

The IP Version 6 Addressing Architecture, IETF datatracker.ietf.org/doc/html/rf…

The IPv6 Global Unicast Address Format, IETF datatracker.ietf.org/doc/html/rf…

Internet Protocol Version 6 Address Space IANA www.iana.org/assignments…

The IPv6 chapter 3 introduces (summary) Oracle Corporation docs.oracle.com/cd/E19253-0…