Shulou(Shulou.com)06/01 Report--

First, the purpose of subnetting:

Meet the needs of different networks for IP addresses to achieve hierarchical network savings of IP addresses

Second, the idea of subnetting:

# 1. 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.

# 2. Concrete 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"

3. Tasks for subnetting:

# ①, determine the length of the subnet mask.

②, determine the range of available addresses for hosts under the subnet (the first available IP and the last available IP).

③, determine the network address (host bits are all 0) and broadcast address (host bits are all 1) cannot assign computer hosts

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

# divide 192.168.1.0 Compact 24 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.

4. VLSM (variable length subnet mask)-allows subnets to continue to be divided into smaller networks

# as shown in the figure: a 192.168.100.0 / 24, divided into two network segments, 192.168.100.0 / 25 192.168.100.128 / 25

We can continue to divide the 192.168.100.128-192.168.100.255 / 25 subnet segment into 192.168.100.128-192.168.100.191 / 26

And 192.168.100.192-192.168.100.255 / 26, and so on.

Fifth, the ultimate case of subnetting (measured) * *

# question: 100.1.32.0Universe 20 divides 5 network segments with 40 hosts in each network segment, reduces host waste, writes subnet mask and host range of each network segment

A: starting with the number of hosts, n represents the number of host bits 2n-2 > = 40 n > = 6, that is, at least 6 host bits can be satisfied, then there are 26 network bits:

100.1.32.0-01100100.000000001.00100000. 00000000

11111111. 11111111. 11110000. 00000000

The original title is 40 hosts, so at least 6 host bits are needed, so the remaining 6 host bits are divided into network bits.

Divide the network segment into 26" 64 network segments, and the number of hosts in each network segment is 26-2 "62:

01100100.000000001.00100000. 00000000- 100.1.32.0

01100100.0000001.0010 0000.01 000000- 100.1.32.64

01100100.0000001.0010 0000.10 000000- 100.1.32.128

01100100.000000001.0010 0000.11 000000- 100.1.32.192

01100100.000000001.0010 0001.00 000000- 100.1.33.0

Subnet mask:

1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

The available hosts for the five network segments that are converted to binary are:

1Mui Musi 100.1.32.1Mube 100.1.32.62 / 26

2MUTHULAMUR: 100.1.32.65-100.1.32.126 / 26

3MUTHUMUTHUMAL 100.1.32.129-100.1.32.190 / 26

4Mutual Mutual 100.1.32.193-100.1.32.254 / 26

5Mui Mui Mui 100.1.33.1 Mustang 100.1.33.62 / 26

6. IP address aggregation (aggregation)

Summary of ideas:

# 1. Convert ip address and subnet mask to binary

# 2. Do the 'and' operation between the binary ip address and the subnet mask, and decimal the answer to get the network address.

# 3. Reverse the subnet mask in binary form

# 4. Take the 'inverse' subnet mask and the ip address to do the 'and' operation, decimal the answer to get the host address.

Examples are as follows:

# suppose there is an IP address: 192.168.0.1

# Subnet mask: 255.255.255.0

# into binary: 11000000.10101000.00000000.00000001

# Subnet Mask 111111111111.11111111.00000000

# and the two are calculated as follows: 11000000.10101000.00000000.00000000

# convert it to decimal: 192.168.0.0

# this is the network address of the above ip, the host address, and so on.

VII. Summary and skills

# a) Summary of binary conversion

# b) Summary of subnetting

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