DHCP Server notes

1 , DHCP protocol (Dynamic Host Configuration Protocol): Dynamically assigning IP addresses to client computers and setting up other network information, network administrators can centrally manage and automatically assign IP addresses in the network, effectively saving IP addresses;

2 , three IP assignment policies:

(1) Manual allocation: mainly in a manual way for a specific computer binding fixed IP address, such as WWW server, FTP server, etc.;

(2) Automatic assignment: When the DHCP client host obtains the IP address from the DHCP server for the first time, this address is permanently assigned to the client host, which can cause the IP address to be wasted;

(3) Dynamic allocation: The only way to automatically re-use the IP address, DHCP for each assigned IP address set a lease, temporarily assign the IP address to the client host use, lease period will take back the IP address, if the client host also needs an IP address, You can then apply to the DHCP server;

3 the process of acquiring an IP address dynamically:

(1) The client sends a DHCPDISCOVER message to the network with a destination IP address of 255.255.255.255, which is the network broadcast;

(2) when the server side receives, based on the assigned priority, an IP address is chosen from the Unassigned IP address range, along with other TCP/IP network settings (gateways, DNS, subnet masks, etc.) to be returned to the client through the DHCPOFFER message;

(3) when there are multiple DHCP servers, the client receives only the one that is returned first, and sends the DHCPREQUEST message in the form of a broadcast, telling it to use that IP address, checking whether the query is repeated, and if duplicate is found, sends a DHCPDECLINE message to the server, Reject its IP address and then re-broadcast it;

(4) when the server receives the DHCPREQUEST message, the selected server will return a DHCPACK message for confirmation, remove the IP address from the allocated IP address range, and end the process; Other unused IP addresses will be recycled;

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DHCP Server notes