1. Network:
It is composed of several nodes and links
1. Node:
2. Equipment (nodes): terminal equipment: provided to users Network services
Network equipment: providing services to users
3. Link: twisted pair, optical fiber
2. OSI/RM: Network Communication Model
Open Systems Interconnection Reference System
ISO (International Standardization)
Top-down packaging process
Bottom-up is the process of unblocking
(1) Physical layer
1. Wire sequence of twisted pair
T568A
Green white, green, orange white, blue, blue white, orange, brown white, brown
T568B
Orange and white, orange, green and white, blue, blue and white, green, brown and white, brown
T568B-------T568B straight-through cable
T568A-------T568B crossover cable
2. Signal transmission mode
Simplex: One end can only send data, and the other end can only receive data
Half-duplex: At the same time, one end can only send data, and the other end can only receive data< /span>
Full duplex: Data can be sent and received at the same time at any time
(2) Data link layer
Provide reliable data transmission services over unreliable links
Data frames
Provide physical addressing
1. MAC address (each network card has an independent MAC address):
48-bit binary
View MAC address under Windows
Operation: Windows+r—cmd
+ipconfig/all
Physical address: MAC
2. Data frame
Preamble: is an identifier, the beginning of a data frame
Destination MAC address: MAC address of the data receiving end
Source MAC address: data MAC address of the sender
Type: Protocol type
Data'
Frame check sequence: FCS
When the data is sent, the data is checked and calculated to get a bit
. After the data is received, the data is checked and calculated to get the new value
If the newly obtained value is consistent with the previously obtained value, it means that there is no problem in the transmission process
(3) Network layer
Logical addressing
1.IP addressing
IP protocol: IPv4, IPv6
The IPv4 address has a total of 32 binary bits. The 32-bit binary is divided into 4 segments, each segment is 8 bits, separated by "," , this method is called the "dotted decimal" method
Convert decimal to binary: divide by 2 and take remainder
2.IP address classification
(1.) Classified address
Determine which category the address is in based onthe size of the first byte
where the address in category A is Class B addresses are allocated to large-scale networks
Class B addresses are allocated to large-scale networks
Class C addresses are allocated to small-scale networks Class E addresses are reserved for experiments
Class D addresses are multicast addresses
(2.) Classless address
The length of network bits and host bits can be customized
mask
is used to determine the length of the network bit, a binary number, 1 represents the network bit, 0 represents the host bit
192.168.1.1~255.255.255.0
(3.) Reserve IP address
The address with all host bits 0 cannot be assigned to the host
192.168.1.0/24
The address with all host bits 1 is not available – before sending Used when broadcasting messages and cannot be assigned to a specific host
192.168.1.255/24
Available addresses: 192.168.1.1/24~192.168.1.254/ 24
(4.) Private address
Private addresses can only be used within the local LAN and cannot be used in the WAN
A: 10.0.0.0~10.255.255.255
B ：172.16.0.0~172.16.255.255
C:192.168.0.0~192.168.255.255
(5.) Public address
Can be used in local LAN or WAN
Walkthrough:
It is known that the IP address of a certain PC is 10.1.1.72/ 28. Please write down the network number, mask, broadcast address and effective address segment of the PC IP address
00001010.00000001.00000001.01001000
Network number: 10.1.1.64 /28
Mask: 255.255.255.128+64+32+16/28
Broadcast address: 10.1.1.64+8+4+2+1/28
Valid address segment: 10.1.1.65~10.1.1.78/28
Exercise 2: It is known that a certain network number is 192.168.15.0/26, please write this Broadcast address and valid address segment within the network number
192.168.15.63/26
Valid address 192.168.15.1~192.168.15.62/26
3. The composition of the IP address: network bit + host bit
Classy
| category | network bit | Host bit | other |
|---|---|---|---|
| A | Top 8 | Last 24 digits | Theoretically available is 2^24 |
| B | 16 bit | 16 bit | |
| C | Top 24 | Last 8 digits |
4.VLSM CIDR
VLSM: Variable length subnet mask (subnetting)
Example: 192.168.1.0/24 is allocated to 100 host bits
One , determine the host bit length: 2^n-2>=100–n=7
11000000.10101000.00000001.00000000
Network number: 192.168.1.0< a i=5> Subnet mask: 255.255.255.128 Broadcast address: 192.168.1.127 Effective address CIDR: ( Classless inter-domain routing summary) Summarize multiple small networks into one large network 192.168.0.0/24 192.168 .1.0/24 192.168.2.0/24 192.168.3.0/24
(4) Transport layer
Function: Used to establish a connection (dialogue between A and B)
| TCP features | Reliable, slow (reliable transmission) | SYN: Original packet ACK: Reply packet |
|---|---|---|
| UDP features | Fast, unreliable (best effort transmission) |
Port number:
Used to distinguish the traffic of different programs with the same IP address
(5), upper three floors:
Session layer: Establish, maintain, and manage sessions between applications
Presentation layer: Data decoding and encoding, data encryption and decryption, data compression and decompression a>
Application layer: Provides interfaces for application software so that applications can use network services. It is the layer that users directly contact
3. Management methods of network equipment
(1) Out-of-band management
Connect through the console port
Steps:
1. The PC-side connection interface is RS232, and the network device-side connection interface is console
2. Log in to the device through terminal, bit rate Set 9600
3. When asked about the device initialization configuration, enter no
4. If there is no device prompt, type Enter and press Router>
5.Router>sh pri to view the current privilege level
6.Router>enable #Enter privilege mode to obtain level 15 permissions
router #：
View the device version information: #show version
View the device running configuration: #show running-config
Enter the configuration terminal (global configuration mode): #conf t #
How to exit quickly:
end: Exit directly from any high-privilege mode to # mode router#reload router#wr #Save device configuration Router（config-line）# login#Enable password Router（config-line）#password gmm #Set console password Router (config)#line console 0Enter console configuration The purpose of setting console password is to verify the identity of the console user Setting of console password: Space : Output content page by page Enter: Exit content line by line –more–
exist: Exit step by step
User Access Verification
Password:(gmm)
Router (config-line)#exec-timeout 0#Close timeout
Router（config-line）#hostname R1#Modify the device hostname for easy identification
Router（config-line）#
The system comes with it of
RT45-RS232
(2) In-band management
R1（config）#int g0/0
R1（config-if）#ip add 192.168.1.1-255.255.255.0
R1（config-if）#no sh#打开接口
4. Device IOS update
1. Ensure the reachability from the router to the server
Router#ping 192.168.10.100
!!!
2. Enable TFTP service on the server side
3. Check the system IOS name through dir
Router#dir
Directory of flash0:/
3 -rw- 33591768 c2900-universalk9-mz.SPA.151-4.M4.bin
4. Copy
Router#copy flash: tftp:
Source filename []? c2900-universalk9-mz.SPA.151-4.M4.bin # The name of the source file that needs to be backed up
Address or name of remote host []? 192.168.10.100 # Remote TFTP server address
Destination filename [c2900-universalk9-mz.SPA.151-4.M4.bin ]? 2023626.bin # Copied file name
1 1. Ensure the connectivity between the device and the TFTP server
2 Router#ping 172.16.1.100
3
4 2. Copy the IOS on the remote server to the local computer through TFTP on the router
5 Router#copy tftp: flash:
6 Address or name of remote host []? 172.16.1.100
7 Source filename []? c2900-universa1k9-mz. SPA.155-3. M4a. bin
8 Destination filename [c2900-universa1k9-mz. SPA.155-3. M4a. bin]? new. bin
9
10 3. Delete the original IOS of the device
11 Router#delete flash:
12 Delete filename []?2800nm-advipservicesk9-mz.151-4. M4. bin
13 Delete flash:/2800nm-advipservicesk9-mz.151-4. M4. bin?
[confirm] Enter
5. Routing basics
Routing: refers to a path from source to destination
Router#show ip interface brief
View the ip address and status of the router's interface< /span> In the network device environment, the default value is 128 TTL value in Windows In the environment, the default value is 64 Time to live, maximum lifetime, 128 TTL C: direct route, Indicates that a network is connected to a certain interface The router forwards the data according to the local router table The gateway needs a Precise address, this address is the interface address of the terminal device connected to the router Gateway: the gateway from one network to another network
show ip route View the routing table of the device