DHCP principle and configuration

Catalog

One 、 What is? DCHP service

1.1DHCP (Dynamic HostConfiguration Protocol, Dynamic Host Configuration Protocol )

1.2 Use DHCP The benefits of

1.3DHCP The way of distribution

Two 、DHCP Lease process

​ edit 1、 Client requests IP Address

2、 Server response

3、 Client selection IP Address

4、 The server determines the lease

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Two 、 Why use DHCP

DHCP The way of distribution

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One 、 What is? DCHP service

1.1DHCP (Dynamic HostConfiguration Protocol, Dynamic Host Configuration Protocol )

• from lnternet Task team design and development         
• Used exclusively for TCP/IP Computers in the network automatically assign TCP/IP Protocol of parameters

 

1.2 Use DHCP The benefits of

• Reduce the workload of Administrators · Avoid the possibility of input errors
• avoid IP Address conflict
• When changed IP Address segment , There is no need to reconfigure each user's IP Address
• Improved IP Address utilization
• Facilitate client configuration

1.3DHCP The way of distribution

• Automatically assigned : Assigned to a IP Permanent use after address
• Manually assign : from DHCP The server administrator specifically specifies lP Address
• Dynamic allocation : Release the after use IP, For other clients

Two 、DHCP Lease process

• Client from DHCP Server get IP The process of addressing is called DHCP Lease process

There are four steps ：

1、 Client requests IP Address

• When one DHCP When the client starts , The client has not IP Address , So the client has to go through DHCP Get a legal address
• here DHCP The client sends... By broadcast DHCP Discover Find information to look for DHCP The server

2、 Server response

• DHCP The server received a request from the client IP Address information when , In their own IP Check the address pool to see if there is any legal IP Address to client
• If there is ,DHCP The server will IP Mark the address , Add to DHCP Offer In the news of , Then broadcast a DHCP Offer news  

3、 Client selection IP Address

• DHCP The client receives the first DHCP Offer Extract... From the message IP Address , issue IP Address of the DHCP The server keeps the address , In this way, the address can no longer be assigned to another DHCP The client

 

4、 The server determines the lease

• DHCP The server receives DHCP Request After the news , With DHCPACK Broadcast a successful acknowledgement to the client in the form of a message , The message contains IP Valid lease and other configurable information for the address
• When the client receives DHCP ACK When the news , To configure IP Address , complete TCP/IP The initialization

Four message sending methods :
If it's Huawei equipment
2 Broadcast 2 Unicast
All other devices broadcast

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• When DHCP The server rents to the client IP The lease term of the address reaches 50% when , It needs to be updated
  The lease term reaches 50% (T1） when ,DHCP The client will automatically unicast to DHCP Server send DHCPREQUEST message , Request an update IP Address lease . If you receive DHCP The server responded DHCP
  ACK message , The lease term is updated successfully ( That is, the lease term starts from 0 Start calculating ); If you receive DHCP NAK message , Then resend DECP DITSCOVER Message request new IP Address
• When the lease term reaches 87.58(T2） when , If not yet received DRCP The response from the server ,DPCP The client will automatically broadcast to DHRCP Server send DRCPREQUEST message , Request an update IP Address lease . If you receive DHCP The server responded DHCP
  ACK message , The lease term is updated successfully （ That is, the lease term starts from 0 Start calculating )﹔ If you receive pHCcP NAK message , Then resend DHCPDISC0NER Message request new 12 Address
• The client sends directly to the server that provides the lease DHCP Request package , Request to update the existing address lease

Two 、 Why use DHCP

avoid IP Address conflict .
When the network changes F Address segment , There is no need to reconfigure each user IP Address . Improved IP Address utilization .
Facilitate client configuration .
DHCP The service avoids manual setting IP Address error , At the same time, it also avoids putting a IP Address conflicts caused by address assignment to multiple workstations .DHCP Provides security 、 Reliable and simple TCP/IP Network settings , Reduced configuration effort P The burden of address

DHCP The way of distribution

Automatically assigned : Assigned to a IP Permanent use after address
Manually assign : from DHCP The server administrator specifically specifies IP Address
Dynamic allocation : Release the after use IP, For other clients