Server maintenance experience talking about graphics DHCP troubleshooting

First, Concept chapter

In the introduction of troubleshooting DHCP before the first to clarify a few conceptual things, only theoretical enrichment, in order to better understand the following troubleshooting ideas.

First: What data can the DHCP service provide? The DHCP service is not omnipotent, he can only provide network-level-related parameters, such as IP address, mask address, gateway address, WINS and DNS server addresses. Information such as MAC addresses is not available for lower-level addresses. The MAC address is burned in a computer network card.

Second: can multiple DHCP servers run at the same time? The DHCP server sends network information to the client through broadcast packets, so if there are more than one DHCP server in the same broadcast domain in the same network, each server provides its own network information, which causes the conflict of broadcast packets in the network. The client does not know which DHCP server to accept the information sent by. So Microsoft sets the default. Only one DHCP server can exist in a broadcast domain network, and DHCP will not work if it is set up or enabled.

Third: What is the lease? The number of days that a lease will be set during the configuration of a DHCP server, what is a lease? After the DHCP server sends the Network Information assignment packet to the client, it receives a reply packet from the client. The DHCP server then establishes a corresponding relationship between the assigned IP address and the MAC address of the computer received from the client, and stores the corresponding relationship in the lease pool of the DHCP server.

Why do we need this lease pool? On the one hand, the next time to allocate network parameter information increased speed. However, if the client computer for the MAC address entry is moved elsewhere or the MAC address changes, if the corresponding relationship established above is kept in the DHCP server's lease pool, the number of available IP addresses is reduced and many valid addresses are consumed by the invalid Mac, So Microsoft introduced the concept of leases. Through the lease we can force every time the DHCP server's lease pool to save the corresponding entries, so as to prevent illegal MAC address commandeer legitimate IP phenomenon.

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