How to plan and design IP addresses (iii)

Nine, internal network dedicated IP address planning and Network address translation Nat method

(1) The basis for selecting the private IP address of the internal network

RFC1918 when discussing the private IP address planning method for the internal network, the preferred party when planning an internal network address system using a private address

The case is using a private IP address block in the Class A address . There are two main reasons "

A) This address covers the space from 10.0.0.0 to 10.255.255.255, the subnet number assigned by the user and the host number

The total length of the 24-bit , can meet the needs of a variety of private networks.

b) A class of private address features are more obvious, since the 1980s, 10.0.0.0 address is no longer used.

As a result, as soon as the address 10.0.0.0 to 10.255.255.255 appears, people will quickly recognize that it is a private address, which facilitates planning and management

Acting Of course, Class B's 16 private address blocks and Class C 256 private address blocks can also be used.

(2) Basic principles for planning the Internal network address system

The basic principles to follow when planning your internal network address system with a private address:

a) concise

Internal network planning must be concise, the documentation is clear, the user is easy to understand. When you see an IP address on a specific device, you don't need to query a lot

Document, you should be able to infer what kind of device it is and its approximate location in the network.

b) Ease of system expansion and management

Internal network planning must consider the implementation of easy, easy management, and can adapt to the future development of the system, has a good scalability.

c) Efficient Routing

The hierarchical address structure is adopted to reduce routing table size and improve routing and packet forwarding speed. Practical experience shows that a well-designed address knot

structure does not but it can improve the performance of the router and improve the efficiency of network management.

(3) Internal network address planning case

A) user needs

1) The company is the headquarters, sales and distribution sub-center, retail stores and other 3-storey structure.

2) The company headquarters backbone Network has 15 LAN, a total of 230 computers and other networked devices

3) The company has a sub-center for sales and distribution management in 18 regions; Each sub-center connects to the headquarters backbone network router via 2 T3 links.

4) Each sub-center has 2 LANs; one for the sub-center of the sales management, one for the sub-center warehouse goods distribution management; Sub-center for sales of pipe

Up to 80 computers, and a maximum of 120 units for the distribution of goods in the center. There should also be a connection within the center of the 2

A central backbone of the LAN with the company headquarters and subordinate retail stores.

5) Each sub-center supports up to 200 grassroots retail stores.

6) Each grassroots retail store has a LAN with a maximum of 12 computers and other networked devices.

The overall network structure is planned for:

b) Basic design ideas

When planning the Internal network address system, the most important is the simplicity and ease of management, while considering the scalability of the system, therefore, the address system design

The basic idea is:

1) Use the private IP address block in Class A to allocate an address with a total length of 24 bits.

2) Adopt 3 level address structure, that is, the total ministerial level-------------level store.

3) The use of fixed-size nets mask.

c) Address structure design

in accordance with the above design idea, according to the actual structure of this example, the simplest and most practical method is to select the Mask 255.255.255.0.

Because the network has more subnets than the number of hosts per subnet, the address structure can be selected as:

1) Network number: 8-bit

2) Subnet Number: 16-bit

3) Host number: 8-bit

Based on the hierarchy of the network, the company headquarters is defined as "area 0", then R is used to indicate the area number in different regions, S is the base sales store

Number, H represents the host number, then the entire company's private IP address structure is: 10.r.s.h. According to this design idea, the IP address of the document can be convenient

Generated.

d) Address Assignment

1) Headquarters LAN address.

The headquarters is defined as Region 0, or r=0, which can 10.0.0.0 represent the company's backbone.

There are 15 LANs in this group, then S equals 1~14.

The address information about the Headquarters LAN connection is shown in the following table:

2) from the headquarters to the responsible sales and distribution management sub-center WAN connection address.

Each sub-center is connected to the headquarters backbone router through 2 T3 links, so you can move two from the backbone router to the responsible sales and distribution management

The two-direction connections in the center are expressed as 10.100+r.0.0 and 10.200+r.0.0 respectively. Then, the Address information table for the headquarters WAN connection is shown in the following table:

3) LAN address for sales and distribution sub-center

in order not to send conflicts with the LAN address of the sales store, the 3 LAN addresses of the sales and Distribution Management Center are represented as: 10.r.255.0, 10.r.254.0 and 10.r.253.0. Then, the address information for the hub is shown in the following table:

4) from the responsible sales and distribution management sub-center to various management is the sales store WAN connection address.

The addresses from the two directions of the sales and distribution management sub-center to the respective managed sales store are represented as: 10.100+r.s.1 and

10.100+r.s.2. Then the address information for the headquarters WAN connection is the address information for the Headquarters LAN connection.

5) Address structure design

6) partition of host address space

Ten, the basic concept of NAT

The NAT technology is used in four types of application areas:

1) address assignment for ISP,ADSL and cable TV

2) Mobile Wireless access address assignment

3) Address assignment of internal network systems, such as e-government intranet, which require strict control over internet access.

4) combined with the firewall

In an internal network designed with a dedicated IP address, if you want to access an external Internet host, the host or router that is running the NAT will have the internal

The IP address is converted to a global IP address.

11, the basic working principle of network address translation NAT

(1) How NAT works

(2) thought: From inside to outside, the source address (private address) is converted to a public address

From outside to inside, the destination address (public address) is converted into a private address.

All of these include the conversion of the port number.

(3) Technical type of NAT

A) static NAT (one-to-one)

b) Dynamic address NAT (one-to-many)

c) Network address port conversion napt (one-to-many, port-differentiated)

12, IPV6 address planning basic method

(1) Key features of the IPV6 address

A) Features: New protocol format, huge address space, effective extension addressing and routing structure, address auto-configuration, sister paper security mechanism, better

To support QoS services.

b) The IPv6 address length is set at 123 bits and can provide 38 IP addresses over 3.4*10.

(2) How to represent IPV6 addresses

A) The 128-bit address of the IPV6 is divided by 16-bit boundaries, each 16-bit segment is converted to 4-digit hexadecimal digits, separated by a colon ":". The result is said to be called

Colon hexadecimal. such as: 21da:0000:0000:0000:02aa:000f:fe08:9c5a.

b) Compression 0\

Some address types contain a series of 0. To further simplify the representation of the IPV6 address, a contiguous 16-bit block that is set to 0 in the colon hexadecimal format

can be compressed to "::". For example, link-local address: FE80:0:0:0:2AA:FF:FE9A:4CA2 can be compressed to: FE80::2AA:FF:FE9A:4CA2.

Multicast address: Ff02:0:0:0:0:0:0:2 can be compressed to: Ff02::2. 0 compression can only be used to compress a contiguous 16-bit segment in a colon hexadecimal symbol,

You cannot use 0 compression to include part of a 16-bit information block.

(3) IPV6 address to be aware of the problem:

A) when using the 0 compression method, it is not possible to compress the effective 0 inside a bit segment.

For example, Ff02:30:0:0:0:0:0:5 cannot be compressed to ff2:3::5.

b):: Double colons can occur only once in an address.

For example: Address 0:0:0:2aa:12:0:0:0, cannot be represented as:: 2aa:12::.

c) Determine: The number of bits that are compressed between 0 is represented. You can count the number of bits in the address, subtract that number by 8, and multiply the result by

16.

For example, Ff02:30:0:0:0:0:0:5 cannot be compressed to ff2:3::5.

b):: Double colons can occur only once in an address.

For example: Address 0:0:0:2aa:12:0:0:0, cannot be represented as:: 2aa:12::.

c) Determine: The number of bits that are compressed between 0 is represented. You can count the number of bits in the address, subtract that number by 8, and multiply the result by

16.

For example, there are 3 bit segments (ff02,3,5) in address ff02:3::5 that can be calculated according to the formula: (8-3) *16=80:: Between 80 bits of 0 is pressed

Shrink.

(4) IPV6 prefix issues

a) The IPV6 subnet mask is used to represent the length of the network and subnet addresses. For example, 192.1.29.7/24 represents a subnet mask length of 24 bits, a subnet mask

is: 255.255.255.0.

b) IPV6 does not support the subnet mask, which supports prefix length notation. Example: 21DA::D 3:2:0/48.

b) IPV6 does not support the subnet mask, which supports prefix length notation. Example: 21DA::D 3:2:0/48.

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How to plan and design IP addresses (iii)