The content of the notes is excerpted from the video of teacher Han Ligang
6.1 Domain Name System DNS
DNS service function: Responsible for resolving domain names and resolving domain names into IP addresses
6.11 What is a domain name
Root.
Top-level domain com edu net cn org gov
Second-level domain 91xuet inhe
Third-level domain dba
6.111 Domain name resolution test
ping www.sohu.com
nslookup www.sohu.com
6.12 Domain name registration process
- Baidu enter domain name registration
- You can use www.xinnet.com for domain name query to see if you want a large domain name registered
If you can log in to QQ normally, but the web page cannot be opened, it may be that there is a problem with your DNS domain name resolution. QQ login, he will log in with the domain name first, but he will log in directly with the IP address if the domain name resolves error.
6.13 The process of domain name resolution
DNS
also has a cache in the DNS server through distributed query . For example, if you want to query www.inhe.net, you first visit the DNS server 101, but he does not care about .net, he will query the upper level root, and the upper level will know it. It will tell 101 this DNS server. Save the DNS address 102 of the .net domain name, then 101 visit 102, 102 tell 101 to visit the IP address of that website, and then 101 tell the client that the client starts to establish a connection and then communicate.
6.14 Install your own DNS server
Several scenarios where you need to install your own DNS server
1. Resolve your own domain name in the intranet
2. Reduce the domain name resolution traffic to the Internet
3. The intranet has a domain environment, and the domain server must be found through DNS, otherwise there is no way to establish a domain environment
Explanation: You can install your own DNS server in the internal network, so that some domain names can be set by yourself, and you are not afraid to repeat with the outside. If you want to access the external network in the internal network, the DNS server you installed can also access the outside To find a DNS server that can resolve the domain name you want to check, as long as the DNS server in your intranet can access the Internet, it can resolve the domain name in the Internet for you.
In the black window, it was found with nslokup, and it prompted an unauthorized response to indicate that it was found from another DNS server.
6.2 DHCP Dynamic Host Configuration Protocol
Static IP address The
computer is relatively fixed and does not need to be moved. We can set a static IP address. A
dynamic IP address is
like a laptop. It needs to move back and forth and assign addresses through DHCP to avoid address conflicts.
6.21 Process of DHCP client requesting IP address
The client will send the information for applying for an IP address to the switch, the switch will broadcast it to all interfaces, and find the DHCP server. At this time, there may be multiple DHCP receipts in the network, and they will select an address from the address pool and provide it to The computer, then the computer will confirm which one it wants, and reply to that DHCP server by sending another packet, and the other DHCP will take back the address it sent.
Your computer must be set to a static address when installing the DHCP server through the windows component
6.22 Assign IP addresses across network segments
How many scopes need to be created to assign IP addresses to how many network segments
6.3 File Transfer Protocol FTP
Active mode: The ftp client tells the FTP server what port to listen
to and establishes a connection with the FTP client’s port. Source port 20
**Passive mode: **The FTP server opens a new port and waits for the FTP client to connect to the
FTP server. If there is a firewall, you need to open ports 20 and 21 to use active mode for data connection
6.4 Remote terminal protocol TELNET
telnet uses port 23 by default
6.5 Remote Desktop Protocol RDP
Graphical interface management
Server multi-user operating system enables remote desktop can be used when multi-use server
XP and windows7 single-user operating system does not support multiple users to log in at the same time
How to map the local hard disk to the remote, so you can transfer local things to the remote
6.6 Hypertext Transfer Protocol HTTP
Website logo, different port, different IP address, different domain name
6.7 Use a web proxy server to access the website
6.71 Scene of using wed server
1. Save the bandwidth of the intranet to access the Internet
2. Use a web proxy to skip the firewall
3. Use a web proxy to avoid tracking
6.8 Email (SMTP, POP4, IMAP)
Mail sending process:
receiving mail requires identity verification, and sending mail generally requires identity verification
6.81 Process and operation of sending and receiving mail
1. Install POP3 and SMTP service and DNS service
2. On the DNS server, create 91xueit.com and 51cto.com to
create host records and mail interaction records
3. Create domain names on POP4 server and create mailboxes
4. Configure SMTP server to create remote domain names *.com allows sending to remote
5. Configure outlookExpress to use POP3 protocol to receive mail
6.82 Build a mail server that can be used on the Internet
1. The domain name MX record is registered on the Internet
2. The mail server has a public IP address or port mapped to the mail server SMTP TCP 25