Four basic IPv4 concepts required before CentOS network configuration

The IPv4 protocol is currently applicable to multiple IP protocols, where v indicates version. 1. IPADDR, that is, IP address: it consists of 32 bits in total. each 8 bits is called a segment and a total of 4 CIDR blocks. The 32bit can be divided into the network part and the host part. The network part is used to distinguish the network segment. the host part is used to distinguish different hosts in the same network segment, with the same network segment, it can be understood as being in the same LAN. The ARP protocol is required for communication between hosts within the same network segment, that is

The IPv4 protocol is currently used for multiple IP addresses.V is version).

 

1. IPADDR, that is, IP address:

A total of 32 bits are composed of four segments, each of which has eight segments. The 32bit can be divided into the network part and the host part. The network part is used to distinguish the network segment. the host part is used to distinguish different hosts in the same network segment, with the same network segment, it can be understood as being in the same LAN. ARP Protocol is required for communication between hosts within the same network segment, that is, Address Resolution Protocol. this Protocol is mainly used to resolve the IP Address to the MAC Address of the NIC, that is, in the same network segment, the communication between hosts is through the MAC address.

For example, host A sends A file to host B, but host A only knows the IP address of host B and the MAC address of host B, therefore, host A Sends this IP address to all hosts in the same CIDR block and requests to communicate with the corresponding host. At this time, host B received data from host A and found that host A was calling itself, so it responded to host A and sent the MAC address to host A. in this way, host A can communicate with host B through MAC.

This ARP protocol triggers a hacker technique, ARP spoofing. However, this technique is only applicable to Lan and does not work on the Internet.

 

2. NETMASK, I .e., subnet mask:

The subnet mask is used to determine the network part of the IP address and the host part. That is to say, the subnet mask can determine whether multiple hosts are in the same network segment.

 

3. GATEWAY, that is, GATEWAY:

It can be understood as the door from one CIDR block to another. That is, all IP addresses in the same CIDR block can access the Internet through it.

 

4. DNS, Domain Name Server, that is, DNS Server and Domain Name resolution Server.

Only when DNS is set can you directly access the Internet with a domain name. For example, 126.com is a domain name, and the com part is used to mark the type of the domain name. net, edu, and org are common examples. Www is the host name, which is generally a web server. Common DNS services include Google 8.8.8.8.