For the intranet computer is able to access through the router, because the router assigned an IP address, so that the computer has an identity, if the router can not be assigned to the computer IP situation, then we have no way to the Internet.
First, the emergence of IP can not be assigned to the phenomenon is most of the client can not log in, can not get IP after login or very slow, in the operating system command prompt in the use of Network command ipconfig, found that the client machine can not obtain IP address, so you can be sure that this reason is not able Restart computer failure Still, prove the problem is not out on the client, to see the switch LED display status is normal, not because of blocking the phenomenon of the crash, then the problem can only be out of the router.
Second, to understand the reason that causes the DHCP server to slow down, it is necessary to understand the work process of the DHCP service. If a DHCP server is deployed on a local area network and the client is set to obtain an IP address automatically, the DHCP client will issue a DHCP Discover packet to the network when it first logs on to the network, when the client discovers that there are no IP data settings on the computer.
Because the client still does not know which network they belong to, so the packet's source address will be 0.0.0.0, and the destination address is 255.255.255.255, and then attach the DHCP Discover information, broadcast to the network.
Third, in Windows presets by default, the DHCP Discover wait time is preset to 1 seconds, which means that the second DHCP Discover broadcast occurs when the client sends the first DHCP Discover packet without a response within 1 seconds. If there is no response, the client will have four DHCP discover broadcasts, except for the first time waiting for 1 seconds, the remaining three wait time is 9, 13, 16 seconds, if none of the DHCP server response, the client will display an error message, declaring DHCP Discover's failure. After that, based on the user's choice, the system will continue to repeat the DHCP Discover process after 5 minutes;
Iv. when the DHCP server receives DHCP Discover information broadcast by a DHCP client, it sends DHCP client offer information, including a leased IP address.
Once the client receives the DHCP offer information, it will use the IP address provided by the server, analyzing from the working process of DHCP, the client cannot obtain the IP address should be the DHCP server does not respond, Or the DHCP server makes a noise, but the client does not receive DHCP Server service information caused by DHCP, the test network cable first after the network hardware cause caused by the client can not receive the DHCP server response, the reason is that the DHCP server did not make a normal response.
Five, the client and the server has a large number of data interaction, which occupies a large number of system resources and network bandwidth, resulting in a corresponding slow DHCP server. This goes into a vicious circle, and in the network is filled with a large number of duplicate requests, which occupy a large number of bandwidth, the formation of a network storm, the server needs to carry out a large number of data transmission, which makes the server network and bus overload, Not only does the operating system process fail to respond to DHCP requests from clients in a timely manner, but computers do not work properly.
Six, it is clear that the overburdened DHCP service has caused the failure. To fundamentally solve the problem, only by upgrading the server or increase the number of servers to do their own duties, so as to avoid overloading the server. That is, deploying specialized DHCP servers for departmental IP services, deploying specialized database servers to serve the online exam system, deploying specialized file servers to provide file servers, and providing network cloning services.
This is mainly because the DHCP function is beyond the limit, it will be like the above router strike, where we especially need to pay attention to, but for a small network, as long as the purchase of a good performance of the router can be, there is no need for a dedicated DHCP server.