What parts does the URL contain, and what does each part do

  • Uniform Resource Locator: URL Uniform Resource Locator. Is a representation of the location and access of resources available on the Internet, with each resource on the Internet having a unique URL.
  • The general syntax format of URL is: protocol :// hostname[:port] / path / [;parameters][? Query]# anchor point

Such as:

  1. The most common protocol is HTTP. HTTP is used to access the network. Other common protocols include HTTPS, FTP, and file.
  2. Hostname, hostname, the name or IP address of the server where the file resides. It can be mapped between domain names and IP addresses through DNS.
  3. [:port], the port number. The client finds the corresponding server based on the IP address (domain name) and the corresponding service provided by the server based on the port number. Different ports correspond to different services. A total of 65535 ports are available. Any TCP/IP service uses ports ranging from 1 to 1023. For example, the default HTTP port number is 80, HTTPS port number is 443, and FTP port number is 21. Both the IP address and port number are indispensable. If the default port number is used, omit it.
  4. Path Indicates the path of resources or files on the host
  5. Parameters Specifies special parameters.
  6. Query Query parameters
  7. Anchor points, anchor point links in HTML (anchor points are not sent to the server)

Nslookup nslookup nslookup nslookup

  • In domain name resolution, the mapping between hosts and IP addresses is configured only on a dedicated DNS server. For devices that need to use host names to communicate on the network, query the IP address of the host on the DNS server. You can obtain the IP address corresponding to the host name

  • Using the nslookup domain name command, you can query DNS records to check whether domain name resolution is normal

  1. Run nslookup to return the default DNS server and IP address. Meanwhile, the command line is in the wait state

  1. Enter a domain name, such as baidu.com, to return to Baidu’s DNS server and Internet address. CTRL + C to exit

  1. Alternatively, enter nslookup baidu.com

What is the function of IP? How does the ping command work

  • Devices connected to the network must have a unique IP address to identify a target
  • There are several special IP’s
  1. 127.0.0.1 indicates the local host
  2. Localhost is added to the hosts file as the alias for 127.0.0.1127.0.0.1 alias To change the alias
  3. 0.0.0.0 does not represent any device
  • Ping in Windows, ping domain name -t
  • There are five steps to using Ping to check connectivity:

1. Run the ipconfig /all command to check whether the local network Settings are correct

  1. Ping 127.0.0.1, 127.0.0.1 Loopback address Ping the loopback address is used to check whether the LOCAL TCP/IP protocol is configured properly.

3. Ping the local IP address to check whether the LOCAL IP address is incorrectly set.

4. Ping the gateway or IP address of the local network to check whether the hardware device is faulty and whether the connection between the local computer and the local network is normal. (This step can be ignored on non-Lans).

  1. Ping domain name Returns the IP address of the domain name

What is a domain name? What are the types of domain names

  • Because IP address is not easy to remember and cannot display the name and nature of the address organization, people design domain name, and use DNS to map domain name and IP address
  • Domain names can be divided into top-level domain names (such as.com), second-level domain names (such as Baidu.com, commonly known as level-1 domain name), and third-level domain names (such as www.baidu.com, commonly known as level-2 domain name).