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DHCP, TFTP Foundation

2022-06-24 08:20:00 【BusyOps】

One 、DHCP relevant

Hard disk was once a very scarce resource in the early days , At that time, diskless workstations were very popular , Each workstation has no operating system , When starting up, you should load the operating system provided by the server into the memory , In order to get the necessary files from the server , There was a protocol called bootp（boot protocol）, It can send a broadcast message to the server for application by means of a network card with self wake-up function IP Address , Then the server sends the operating system files required by the workstation , But its distribution IP The address is permanently assigned . So then it came out DHCP（Dynamic Host Configuration Protocol）, It introduces the concept of lease term

1. Workflow

First step （dhcp discover）： After the client is powered on , Because I don't have IP Address , So pass RARP Broadcast to find DHCP The server
The second step （dhcp offer）： After the server receives the broadcast , Will be assigned to the client IP、MASH、GW、DNS wait
The third step （dhcp request）： Clients may receive multiple messages dhcp Server response , It will select one from multiple servers and send dhcp Request use message , This message is also broadcast , I choose one dhcp The server , And then the unselected dhcp The server reclaims the newly assigned address
Step four （dhcp ack）：dhcp Send a confirmation message , It's also a radio

2. Renewal

50%： When ip Percent of the remaining lease term of the address 50 When , The client will contact dhcp Application for renewal of server , If there is no response, proceed to the next step
75%： When ip Percent of the remaining lease term of the address 75 When , The client will contact dhcp Application for renewal of server , If there is no response, proceed to the next step
87.5%： When ip Percent of the remaining lease term of the address 87.5 When , The client will contact dhcp Application for renewal of server , If there is no response, it will be re initiated dhcp discover

3、 Installation and related documents

The package name is dhcp, Can be used directly yum install dhcp -y install

/etc/dhcp/dhcpd.conf： The configuration file
/etc/dhcp/dhcpd6.conf：ipv6 Configuration file for
/usr/sbin/dhcpd：
/usr/sbin/dhcrelay： Repeater program file
/var/lib/dhcpd/dhcpd.leases：dhcp Distribution record of
/usr/lib/systemd/system/dhcpd.service：Uint file
/usr/lib/systemd/system/dhcpd6.service：Unit file
/usr/lib/systemd/system/dhcrealy.service：Unit file

4、 Configuration related instructions

option domain-name "string"; ： Indicate except IP And mask , Other attributes to be assigned 
option domain-name-servers "string";   ：DNS Server address 
default-liease-time #; ： Default lease term , Unit second 
max-lease-time #; ： Maximum lease term 
log-facility： Define the log

subnet <IP> netmask <MASK> {
             ： Indicate which network segment to be responsible for 
    range <START_IP> <STOP_IP>;      ： Indicate the start and end addresses that can be assigned 
    option routers IP                ： Indicate the assigned gateway address 
}

5、 Sample configuration

option domain-name "busyops.org";
option domain-name-servers 8.8.8.8;
default-lease-time 600;
max-lease-time 7200;

subnet 192.168.70.0 netmask 255.255.255.0 {
    
    range 192.168.70.100 192.168.70.250;
    option routers 192.168.70.254;
}

Two 、TFTP relevant

The full name is simple file transfer protocol （Trivial File Transfer Protocol）, Mainly responsible for the guidance of diskless workstation . You can use it directly yum install tftp tftp-server install