Network Security Learning （ Qianfeng network security notes ）2–IP And basic DOS command

1.IP Address details

LAN （ Intranet ）

Single LAN composition ： Switch , Ethernet cable ,pc
Switch ： A device used to build a local area network for an intranet

IP Address

It's usually 32 Bit binary address
Or in the shape of X.X.X.X The decimal address of （X For the range of 0-255）

Subnet mask

LAN communication rules ： All in the same LAN IP Addresses must be in the same network segment to communicate with each other
IP The composition of the ： Network bit + Host bit ( The network bits are the same IP Address , For the same segment )
Subnet mask ： Used to determine IP Network bit of （255 The corresponding number is network bit ,0 The corresponding number is the host bit ） There are three kinds of ：
255.0.0.0
255.255.0.0
255.255.255.0

Pictured , The host network segment is 192.168.159., Host location is .128. Will host the IP The address and subnet mask can get the network bit of this note by phase and .

IP Address

ISO Define five categories （IP Address first distinguish ）
A class ：1-126 Default mask ：255.0.0.0
B class ：128-191 Default mask ：255.255.0.0
C class ：192-223 Default mask ：255.255.255.0
D class ：224-239 Multicast address
E class ：240-254 Scientific research uses
notes ： At present, we can only use A、B、C class
The subnet mask can be modified
255 Is the broadcast address of the network segment
127.0.0.1 Return address （ Communicate with yourself ）

gateway

An exit to the network , Usually on the router
Router ： Devices connected to the Internet
One of the functions of the gateway is as follows ：pc Contract out
1、 First judge the target IP And whether you are Same segment
2、 If in the same network segment , Then send it directly , Gateway not found
3、 If not in the same network segment , Then contract to gateway

DNS

The domain name system （ service ） agreement （DNS） Is a distributed network directory service , Mainly used for domain name and IP Address translation , And controlling the sending of e-mail on the Internet

Test network connectivity

Resolve the domain name manually ：nslookup website
ping The goal is IP # Test network connectivity , Going back and forth is the way
ping -t The goal is IP # always ping
ping -n Numbers # modify ping The number of bags , The default is 4
ping -l Numbers # modify ping The size of the bag
ipconfig # see ip essential information
ipconfig /all # see ip All the information
basic DOS command
cd… Return to parent directory
cd\ Return to root
d: Get into D disc
cls Clean all dos operation
dir Displays the current drive letter file information

browse files
type file name . Extension Show
type file name . Extension |more Pagination display

create a file
1、echo
2、copy con file name . Extension
Start writing content
ctrl+z Press enter to finish writing

Delete file
del *.txt Delete all txt Final document
del . Delete file

Shut down, restart, log off
shutdown -s -t 100 Timed shutdown
shutdown -s -f -t 100 Timed forced shutdown
shutdown -r -t second Restart regularly
shutdown -a Cancel timing
shutdown -l Cancellation