I. IPv6 IP Address Allocation Principles only mentioned in many reports that IPv6 is relatively widely used IPv4 for the most important difference on IP addresses is that IPv6 uses 128 address, relatively current 32-bit IPv4 address. It is said that there is an incumbent advantage in quantity. However, IPv6 allocates this 128-bit address. How to effectively manage how much reports are reported. The following we describe the address assignment and management of IPv6 by comparison with IPv4.
1. IPv6 address type
The most significant feature of IPv6 is its huge amount of address space, we know that IPv6 uses a 128-bit address length and is four times that of IPv4. At the time of IPv4, there can be 2 ^ 32 or 4,294,967,296 (4 billion) possible IP addresses, but because of these IPs, it is actually a lot of IP addresses that can actually be used. When IPv6 addresses are 128 bits, there will be 2 ^ 128 or 340, 282, 366, 920, 938, 431, 768, 211, 456 possible IP addresses, this astronomical figure is sufficient to make each of the world can allocate 1.8 × 1019 IPv6 addresses. The IPv6 address is an identifier of a stand-alone interface, all IPv6 addresses are allocated to interfaces, not nodes. Since each interface belongs to a particular node, any of the interface addresses of the node can be used to identify a node. The corresponding classification is also made in the IPv6 address, but it is different from the IPv4 classification method, which is mainly divided into the type of transmission through its address prefix, and is divided into three types:
· Unicast Address: Used to identify a single network interface. The target address is a packet of unicast addresses will be sent to a network interface identified by this address.
• Anycast Address: Used to identify a set of network interfaces (usually different nodes). The target address is a packet of the address of the address will be sent to a nearest network interface in the routing sense. Additional communication sites suitable for "One-to-One-of-Many" (one of the pair of groups). The receiver only needs to be one of a set of interfaces. If the mobile user is accessible to the network, it is necessary to access a receiving station closest to the user, so that the mobile user can not be too much in the geographic position. Multi-limit.
· Multicast Address: Used to identify a group of network interfaces (usually different nodes). The packet sent to the multicast address sent to all network interfaces in this group. There is no broadcast address in IPv4 in IPv6, replaced with multicast addresses. This type of IP address is suitable for "one-to -many" communication occasion.
Before you specifically introduce these address types, I will first introduce the "Format Prefix, FP) that determines these IP address types. As the name suggests, the address prefix is the number in the address of the address. Of course, it also belongs to the 128-bit address space range, which represents different address types through different address prefixes. The following table 1 is the meaning representing the address prefix specified in the IPv6 standard.
Note: In addition to the IP address in IPv4, there is also a subnet mask, but it is no longer used in IPv6, IPv6 only supports prefix length representation.
Table 1 IPv6 address prefix allocation
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Address Prefix | Prefix Allocation Status and Significance | Address Prefix | Prefix Allocation Status and Significance --------------------------------------------------------------------------------------------------------------- -------------------------------------------------- --------------------
001 | Can gather global unicast delivery address | 0000 001 | Reserved to NSAP allocation
-------------------------------------------------- -------------------------------------------------- ---
010 | Based on the carrier address | 0000 010 | Unallocated
-------------------------------------------------- -------------------------------------------------- ---
011 | Unall | 0000 011 | Unallocated
-------------------------------------------------- -------------------------------------------------- ---
100 | Geographic address | 1111 110 | Unallocated
-------------------------------------------------- -------------------------------------------------- ---
101 | Unall | 1111 1111 | Multicast Transfer Address
-------------------------------------------------- -------------------------------------------------- ---
110 | Unall | 0000 0000 |
-------------------------------------------------- -------------------------------------------------- ---
0001 | Unall | 0000 0001 | Unallocated
-------------------------------------------------- -------------------------------------------------- ---
1110 | Unall | 1111 1110 0 | Unallocated
-------------------------------------------------- -------------------------------------------------- ---
0000 1 | Unall | 1111 1110 10 | Local link address
-------------------------------------------------- -------------------------------------------------- ---
1111 0 | Unall | 1111 1110 11 | Local Areas Unicast Transport Address
-------------------------------------------------- -------------------------------------------------- --- 1111 10 | Unall | |
-------------------------------------------------- -------------------------------------------------- ---
2. Unicast address
An IPv6 unicast address is associated with a single interface, and the package transmitted to the unicast address is sent to a single interface identified by the address. However, in order to satisfy the load balancing system, multiple interfaces are allowed in the RFC 2373 to use the same address as long as these interfaces appear in the implementation. The IPv6 unicast address is aggregated after using a continuous bit mask, which is similar to the non-type domain field of the IPv4 (CIDR: Classless Inter-Domain Routing).
Unicast addresses are divided into: AggRegatable Global Unicast Addresses, NSAP Address, IPX Hierarchy Addresses, NSAP Address, Site-local Address, and Link Location (Link-local) Address, etc. All network interfaces must have at least one link local address, and can also have multiple addresses (including unicast addresses, any new addresses, and multicast addresses). The current allocation is mainly the aggregated global unicast address in unicast addresses.
· Can gather global unicast delivery address: As the name suggests that the address can be forwarded globally, it can be seen from Table 1, such address format prefix is "001", which is equivalent to the IPv4 public address. The design of the global address helps architecture a hierarchical routing infrastructure. Unlike the planar and hierarchical mixed routing mechanisms used in IPv4, IPv6 supports more efficient hierarchical addressing and routing mechanisms.
"Fp" is the address prefix (also known as "format prefix"), which is used to distinguish other address types, here it is "001". Subsequently, the 13-bit TLA ID (top aggregate ID number), 8-bit RES (reserved bit, is used in future TLA or NLA expansion.), 24-bit NLA ID (secondary aggregate ID number), 16-bit SLA ID (Node ID) and 64-bit Interface ID (Host Interface ID). TLA, NLA, SLA constitute three network hierarchies arranged under the top of the top, and apply for the ID number to the first level. TLA is a public backbone network access point that is interconnected with long-distance service providers and telephone companies, and its ID is managed by the International Internet Registration Body IANA. NLA is usually a large ISP that applies for addresses from TLA and assigns an address for the SLA. SLA can also be called subscriber, which can be a mechanism or a small ISP. The SLA is responsible for assigning addresses for its subscriber. SLA is usually assigned an address block consisting of continuous addresses for its subscribers so that these institutions can establish their own address hierarchy to identify different subnets. The bottom layer of the hierarchical structure is the network host.
· NSAP (Network Service Access Point, NSAP) Address: called a network service access point address, which is also the address used to retain, and its address prefix fp = 0000 001.
· IPX (fp = 0000 010): This is also used to retain the IP address, and its address prefix is FP = 0000 010. · Site local address: This type of format prefix fp = 1111 1110 11. Equivalent to IPv4 private address space such as 10.0.0.0.0.0.0.0.0/12 and 192.168.0.0/16. For example, enterprise dedicated intranet, if not connected to the IPv6 Internet, then you can use the site local address inside the enterprise site, the valid domain is limited to the inside of a site, the site local address cannot be accessed by other sites, and the package containing such addresses is not Will be forwarded by the router to outside the site. A site is usually agency network or subnet located in the same geographic location. Unlike the link local address, the site local address is not automatically configured, but must be configured with a stateless or full status address.
The site local address allows the company to construct the company's private network without the Internet, without having to apply for an address prefix of a global address space. If the company is in the future to connect into the Internet, it can be combined with a global prefix with a global prefix into a global address with its subnet ID and interface ID. IPv6 automatically recommends.
· Link local address: format prefix fp = 1111 1110 10. Communication between adjacent nodes for the same link, such as communication between the host when there is no router on a single link. The link local address is equivalent to the current APIPA IPv4 address currently using 169.254.0.0.0.0/16 prefix under Windows, which is limited to local links. Link local addresses can be used for neighbor discovery, and always automatically configure, the package containing link local addresses will never be forwarded by IPv6 routers.
In fact, in addition to several unicast delivery addresses described above, the following class compatible IPv4 standards are also specified in IPv6 standard, which is mainly used for the transition period of IPv4 to IPv6, generally "IPv4 Compatible address "," IPv4 Mapping Address "," 6TO4 Address "three categories.
· IPv4 compatible address: It can be represented as 0: 0: 0: 0: 0: 0: wxyz or :: wxyz (wxyz is an IPv4 address represented by point decimal), used for nodes with IPv4 and IPv6 protocols. IPv6 communicates.
· IPv4 mapping address: Yes, another embedd IPv4 address IPv6 address, can be represented as 0: 0: 0: 0: 0: fff: w.x.y.z or :: fff: w.x.y.z. This address is used to indicate nodes that only support IPv4 addresses.
· 6TO4 Address: Nodes for both protocols with IPv4 and IPv6 communicate in IPv4 routing architecture. 6TO4 is a dynamic tunneling technology that passes IPv6 packets between host and routers through IPv4 routing.
3. Any address
IPv6 Anncast address is assigned to more than one interface (usually different nodes), and any format of any format of the unicast address is allocated from the unicast address space. Thus, from the grammatical, the address and the unicast address are not distinguished. When a unicast address is assigned to more than one interface, it converts it to a new address. The assigned contact with a new address must get a clear configuration, so that it knows that it is an address. Currently, any point transmit address is only used as a target address and is only assigned to the router. Any point delivery address is allocated from a single point transmitting address space, using one of the single-point transmission address format. The address structure is shown in Figure 2.
Subnet-Router Any point transmit address must be predefined, which is generated from the subnet prefix. To construct a subnet-router arbitrarily transfer address, the subnet prefix must be fixed, the remaining bit number is full "0". All router interfaces in one subnet are allocated subnets of the subnet - router arbitrarily transmitted addresses. Subnet - Router Any point of transfer address for a set of routers communications with the remote subnet.
For any any of the new address, there are longest address prefix P, which defines a topology area, all interfaces that belong to the address of the address are in this area. In this area defined in P, each member belonging to the set of address sets must be advertised as a separate entry in the system; outside of this area, the anycast address may aggregate to the prefix. P The search advertisement. 4. Multicast Address
IPv6 multi-point transfer address format prefix is 1111 1111, and it also includes fields such as flags, range fields, and group IDs, as shown in FIG.
The 4th "Flags" in Figure 3 can be represented as: 000t. Among them, the three reservations must be initialized into 0. T = 0 represents a multi-point transmission address that is permanently assigned by IANA; T = 1 represents a temporary multi-point transmission address. The 4-bit Scope is a multi-point delivery range to limit the range of multi-point transmission. Table 2 lists the Scope field values defined in RFC 2373.
Table 2 IPv6 multicast address SCOPE allocation
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Value | Range | Value | Range
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0 | Reserve | 8 | Institutional Local Area
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1 | Node local range | 9 | Unallocated
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2 | Link local range | A | Unallocated
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3 | Unall | B | Unallocated
-------------------------------------------------- ----------------
4 | Unall | C | Unallocated
-------------------------------------------------- ----------------
5 | Site local area | D | Unallocated
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6 | Unall | E | Global
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7 | Unall | F | Reserved
-------------------------------------------------- ----------------
The "group ID" in Figure 3 is used to identify a multi-point transfer group within a given range. Used to determine a multicast group, within a given area, it can be permanent or temporary. The permanent assigned group ID is independent of the scope domain, and the temporary group ID is only related to a particular range domain.
For permanently assigned multicast addresses, its "meaning" is independent of its area value. For example: assuming a server group is assigned a permanent multicast address of a Group ID 111 (hexadecimal):
· FF01: 0: 0: 0: 0: 0: 0: 111 refers to all servers with the sender in the same node, because the first 8 bits of this server are "1111 1111" specified in the multicast IP address (16) For "ff"), and "Flags" segment, because of the specified permanent, "0000", "0001" in "scope" is the node local area, so the top 16 in this IP address For "FF01", the last "111" is group number, the "0" "0" is supplemented (because the IPv6 address is 128 digits, there is no specified "0" to make up), so that "FF01: 0" : 0: 0: 0: 0: 0: 111 ", press IPv6 to address the address representation method to" FF01 :: 111 ", see the next section. The following IP addresses are also understood. · FF02: 0: 0: 0: 0: 0: 0: 111 refers to all servers with the sender's on the same link;
· FF05: 0: 0: 0: 0: 0: 0: 111 refers to all servers with the sender in the same place;
· FF0e: 0: 0: 0: 0: 0: 0: 111 refers to all NTP servers in the Internet.
For non-permanently assigned multicast addresses, it is only meaningful within a given area. For example: a local multicast address of the non-permanent place of a place is FF15: 0: 0: 0: 0: 0: 0: 0: 111, the group is independent of the group of the same address in different places, with the same group ID in different regions. The non-permanent group is independent of, which is independent of the permanent group using the same Group ID. Multicast addresses can never be used as the source address of IPv6, or used as any designer.
5. IP address can be obtained by host and router
In IPv4, if a host installs a network card, the typical situation is that the host has an IPv4 address assigned to the NIC. But IPv6 is different, usually an IPv6 host has multiple IPv6 addresses, even if the host has only one single interface. One IPv6 host can have the following single point transmission address at the same time:
· Link local address for each interface
· Single point delivery address of each interface (single point transmission address of the interface can be a site local address and one or more gathering global addresses)
· Loopback interface of the loop (: 1)
There are at least two addresses of a typical IPv6 host: (1). The link local address (2) of the local link information is received. The routed site local address or global address. In addition, each host also needs to keep listening to the information flow on the following multi-point transfer address:
· Nodes all node multicast addresses in the local area (ff01 :: 1)
· All node multicast addresses in the link (FF02 :: 1)
· Solicited-Node multicast address (if an interface of the host is added to the request node group)
· Multi-point transfer address (if an interface of the host is added to any multicast group)
And an IPv6 router can be assigned to the following unicast addresses:
· Link local address for each interface
· Single point delivery address of each interface (single point transmission address of the interface can be a site local address and one or more gathering global addresses)
· Subnet - router free point delivery address
· Others send addresses (optional)
· Loop address of the loop interface (: 1)
Similarly, in addition to these addresses, the router needs time to keep listening to the information flow on the following multi-point transfer address:
· All node multicast addresses in nodes (ff01 :: 1)
· All routers in node local range (ff01 :: 2)
· All node multicast addresses in the link local area (ff02 :: 1)
· All routers in the link (FF02 :: 2) · All routers in the site local area (FF05 :: 2)
· Solicited-Node multicast address (if an interface of the router is added to the request node group)
· Multicast group multi-point transmission address (if an interface of the router is added to any multicast group)
