Theory + experiment-(Linux network) DHCP principle and configuration

1. Understand DNCP service

Benefits of using DHCP:

• Reduce the workload of administrators
• Avoid the possibility of input errors
• Avoid IP address conflicts
• When changing the IP address segment, there is no need to reassign each user's IP address
• Improved utilization of IP addresses
• Convenient client configuration

DHCP distribution method:

• Automatic allocation: permanent use after being allocated an IP address
• Manual allocation: the IP address is specified by the DHCP server administrator
• Dynamic allocation: release the IP after use, for other clients to use

Two, DHCP lease process

Three, DHCP server configuration

Four, DHCP client configuration

Five, DHCP relay principle and configuration

DHCP configuration file

vi /etc/dhcp/dhcp.conf

ddns-update-style none;
subnet 192.168.100.0 netmask 255.255.255.0 {
    
    
range 192.168.100.100 192.168.100.200;
option routers 192.168.100.1;
option subnet-mask 255.255.255.0;
option domain-name "www.bdqn.com";
option domain-name-servers 114.114.114.114 8.8.8.8;
option broadcast-address 192.168.100.255;
default-lease-time 21600;
max-lease-time 43200;
host prtsvr {
    
    
hardware ethernet 00:0C:29:BC:CF:2F;   ###第二台客户机的MAC地址
fixed-address 192.168.100.66;
  }
}

#ddns-update-style none;
subnet 192.168.10.0 netmask 255.255.255.0 {
    
    
range 192.168.10.100 192.168.10.200;
option routers 192.168.10.1;
option subnet-mask 255.255.255.0;
option domain-name "www.bdqn1.com";
#option domain-name-servers 114.114.114.114 8.8.8.8;
#option broadcast-address 192.168.100.255;
default-lease-time 21600;
max-lease-time 43200;
#host prtsvr {
    
    
#hardware ethernet 00:0C:29:BC:CF:2F;   ###第二台客户机的MAC地址
#fixed-address 192.168.100.66;
#  }
}

#ddns-update-style none;
subnet 192.168.20.0 netmask 255.255.255.0 {
    
    
range 192.168.20.100 192.168.20.200;
option routers 192.168.20.1;
option subnet-mask 255.255.255.0;
option domain-name "www.bdqn2.com";
#option domain-name-servers 114.114.114.114 8.8.8.8;
#option broadcast-address 192.168.100.255;
default-lease-time 21600;
max-lease-time 43200;
#host prtsvr {
    
    
#hardware ethernet 00:0C:29:BC:CF:2F;   ###第二台客户机的MAC地址
#fixed-address 192.168.100.66;
#  }
}

Topology configuration

SW2

<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]sysname SW2
[SW2]v b 10 20 30
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW2]int e0/0/1
[SW2-Ethernet0/0/1]p l a
[SW2-Ethernet0/0/1]p d v 10
[SW2-Ethernet0/0/1]un sh
Info: Interface Ethernet0/0/1 is not shutdown.
[SW2-Ethernet0/0/1]int e0/0/2
[SW2-Ethernet0/0/2]p l a
[SW2-Ethernet0/0/2]p d v 20
[SW2-Ethernet0/0/2]un sh
Info: Interface Ethernet0/0/2 is not shutdown.
[SW2-Ethernet0/0/2]int e0/0/3
[SW2-Ethernet0/0/3]p l a
[SW2-Ethernet0/0/3]p d v 30
[SW2-Ethernet0/0/3]un sh
Info: Interface Ethernet0/0/3 is not shutdown.
[SW2-Ethernet0/0/3]int g0/0/1
[SW2-GigabitEthernet0/0/1]p l a
[SW2-GigabitEthernet0/0/1]p l t
[SW2-GigabitEthernet0/0/1]p t a v a
[SW2-GigabitEthernet0/0/1]un sh
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[SW2-GigabitEthernet0/0/1]q
[SW2]

RSW1

<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]sysname RWS1
[RWS1]dhcp enable 
Info: The operation may take a few seconds. Please wait for a moment.done.
[RWS1]v b 10 20 30
Info: This operation may take a few seconds. Please wait for a moment...done.
[RWS1]int g0/0/1
[RWS1-GigabitEthernet0/0/1]p l t
[RWS1-GigabitEthernet0/0/1]p t a v a
[RWS1-GigabitEthernet0/0/1]un sh
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[RWS1-GigabitEthernet0/0/1]q	
[RWS1]int Vlanif 10
[RWS1-Vlanif10]ip add 192.168.10.1 24
[RWS1-Vlanif10]dhcp select relay 	
[RWS1-Vlanif10]dhcp relay server-ip 192.168.100.10
[RWS1-Vlanif10]q	
[RWS1]int Vlanif 20
[RWS1-Vlanif20]ip add 192.168.20.1 24
[RWS1-Vlanif20]dhcp select relay 
[RWS1-Vlanif20]dhcp relay server-ip 192.168.100.10
[RWS1-Vlanif20]q	
[RWS1]int Vlanif 30
[RWS1-Vlanif30]ip add 192.168.100.1 24
[RWS1-Vlanif30]q
[RWS1]ping 192.168.100.10
  PING 192.168.100.10: 56  data bytes, press CTRL_C to break
    Reply from 192.168.100.10: bytes=56 Sequence=1 ttl=64 time=50 ms
    Reply from 192.168.100.10: bytes=56 Sequence=2 ttl=64 time=50 ms
    Reply from 192.168.100.10: bytes=56 Sequence=3 ttl=64 time=50 ms
    Reply from 192.168.100.10: bytes=56 Sequence=4 ttl=64 time=60 ms

  --- 192.168.100.10 ping statistics ---
    4 packet(s) transmitted
    4 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 50/52/60 ms

[RWS1]ping 192.168.100.10
  PING 192.168.100.10: 56  data bytes, press CTRL_C to break
    Reply from 192.168.100.10: bytes=56 Sequence=1 ttl=64 time=110 ms
    Reply from 192.168.100.10: bytes=56 Sequence=2 ttl=64 time=70 ms
    Reply from 192.168.100.10: bytes=56 Sequence=3 ttl=64 time=60 ms
    Reply from 192.168.100.10: bytes=56 Sequence=4 ttl=64 time=50 ms
    Reply from 192.168.100.10: bytes=56 Sequence=5 ttl=64 time=50 ms

  --- 192.168.100.10 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 50/68/110 ms