Shulou(Shulou.com)06/02 Report--

IP address: the unique address of linked network devices and computers on the Internet, which is used as the unique identification of the host on the Internet, called the IP address. IP addresses are made up of 32-bit binary (32bit)

The IP address consists of two parts: the network part and the host part.

Network part (NET ID): distinguishes whether the IP address belongs to the same network segment. Use binary (1) to represent the network part

Host part (HOST ID): the identification of a node in the network. Use binary (0) to represent the host part

For example, 192.168.0.25 192.168.0 is the network part and the last 25 is the host part.

IP addresses are divided into five categories: A B C D E

Class An address: 1-126 subnet mask: 255.0.0.0

Class B address: 128-191 Subnet Mask: 255.255.0.0

Class C address: 192-223 subnet mask: 255.255.255.0

AME Class C addresses are commonly used.

Class D address: 224-239 Multicast address (unicast Multicast broadcast)

Class E address: 240-255 research address (scientific research)

Dmure class E addresses are not commonly used

Some of the other network addresses that are not used on the Intermet are private addresses. Private addresses are generally suitable for enterprise users to use on the internal network.

Private addresses include: class An addresses: 10.0.0.0Murray 10.255.255.255

Among the category B addresses are: 172.16.0.0 Murray 172.31.255.255

Among the class C addresses are: 192.168.0.0Murray 192.168.255.255

Overview and function of Subnet Mask

The subnet mask is a 32-bit binary value applied to TCP/IP networks, with 8 bits per section, which must be used in conjunction with IP addresses.

The subnet mask 32 bits all correspond to the 32 bits of the IP address. If a bit is a network address, the subnet mask is 1, otherwise it is 0.

The subnet mask can be calculated with the IP address to separate the network address and the host address in the IP address, which can be used to determine whether the IP address is on the local area network or the wide area network.

Subnet masks are generally used to further divide the network into several subnets to avoid excessive host congestion or IP waste.

Classification of subnet masks:

The subnet mask 32 bits corresponds to the 32 bits of the IP address. If a bit is a network address, the subnet mask is 1, otherwise it is 0. For example, for a class An IP address, the first section is the network address and the other three sections are the host address, so the mask is "11111111.00000000.00000000.00000000".

Class An address default subnet mask: 255.0.0.0 (8 bits)

Class B address default subnet mask: 255.255.0.0 (16 bits)

Default subnet mask for Class C address: 255.255.255.0 (24 bits)

IP addresses can be divided into two categories: classful addresses and classless addresses

Classful address: A B C class 3 address belongs to classful address.

Classless address: subnetting ip addresses, the divided IP addresses no longer have the characteristics of classful addresses, these addresses are called classless addresses.

Ideas for subnetting:

Step: when we create / subnetting, it must be created according to certain requirements, which is our actual network requirements.

In general, we follow these steps to identify our network needs:

(1) determine the number of hosts required for each subnet:

One for each host

One per router interface.

(2) determine the number of network ID required: (network segment)

One per LAN subnet

One for each WAN connection.

(3) according to the above requirements, the following contents are determined:

A subnet mask for the entire network

Unique subnet ID for each physical network segment

The host range for each subnet.

Specific division:

1. Borrow the "network bit" part of the original classful network IPv4 address to the "host bit" part.

2. Change some bits that originally belong to the "host bit" into a part of the "network bit" (usually called "subnet ID").

3. The original "network bit" + "subnet bit" = the new "network bit". The length of "subnet ID" determines the number of subnets that can be divided.

The number of "subnet bits" in the new IP address; that determines the maximum number of "subnets"

Tasks for subnetting:

Determine the length of the subnet mask.

Determine the range of available addresses for hosts under the subnet (the first available IP and the last available IP).

Make sure that the network address (host bits are all 0) and broadcast addresses (host bits are all 1) cannot be assigned to computer hosts

III. The case of subnetting in Class C network-- the corresponding table of subnet mask and related parameters

For example, 192.168.1.0 Compact 24 is divided into 4 small network segments

The host bit is divided into two bits to the network bit: the network bit is changed into 26 bits, the host bit is 6 bits, and the network segment is divided into 22 segments. There are 26,664 hosts in each network segment.

Note:

In general, the mask of / 31 is not applicable, while the mask of / 32 is generally used as the device management address when configuring the Lookback interface address, so the address can be saved.

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