Recently, the author encountered two uncommon network failures during the maintenance of the school network, but it was very interesting and felt that it was necessary to take them out for your reference.
The first case failure: The client cannot obtain its TCP/IP configuration automatically from the DHCP server immediately
Our school’s IP address, DNS and gateway are automatically obtained through the DHCP server. Some time ago, the school leaders felt that the Internet access through the education metropolitan area network was not fast enough, so they decided to access the Internet directly through the telecommunications dedicated line. In this way, I modified the DNS settings of the DHCP server and restarted the DHCP server. After that, a few teachers told me that their computers could not open the web page, but they could use QQ. After excluding the virus and system reasons, I thought of the DNS problem.
Run the "Ipconfig /all" command and checked. Sure enough, the machine's DNS display is still the previous address, and it did not get updates from the DHCP server in time. Now it's simple. Run the "Ipconfig /releasw" command to release it, and then run "Ipconfig /renew" to reconfigure it. The wonderful web pages are now in front of us again.
The second case failure: The MAC address of the proxy server corresponding to the ARP cache table of the client is incorrect
A very strange network failure occurred on several machines in the school: the machine could access other machines, but it could not access the address of the proxy server (i.e. the address of the gateway) 192.168.0.1, causing the machine to be unable to access the Internet.
Run the "Arp -a" command to check the current ARP item, but find that the MAC address corresponding to the host address 192.168.0.1 is 00-00-00-00-00-00-00, which is not the MAC address of the host at all! Run the "Arp -a 192.168.0.1 00-06-29-ee-08-bf" (correct MAC address) command, add an item in the ARP cache, associate the IP address with the correct physical address, and find that the fault is solved, the computer can ping the host and access the Internet normally.
We know that ARP (Address Reverse Protocol) is used to display or modify the physical address translation table of the Ethernet IP or token ring used. There is an ARP cache table in each computer with TCP/IP protocol installed. The IP address in the table corresponds to the MAC address one by one, while the mapping of the host's IP address to the MAC address always exists in the ARP cache table. However, due to some reasons of the system, the MAC address of the host in the ARP cache table cannot be updated and obtained, which causes the machine to be unable to access the Internet.
The first case failure: The client cannot obtain its TCP/IP configuration automatically from the DHCP server immediately
Our school’s IP address, DNS and gateway are automatically obtained through the DHCP server. Some time ago, the school leaders felt that the Internet access through the education metropolitan area network was not fast enough, so they decided to access the Internet directly through the telecommunications dedicated line. In this way, I modified the DNS settings of the DHCP server and restarted the DHCP server. After that, a few teachers told me that their computers could not open the web page, but they could use QQ. After excluding the virus and system reasons, I thought of the DNS problem.
Run the "Ipconfig /all" command and checked. Sure enough, the machine's DNS display is still the previous address, and it did not get updates from the DHCP server in time. Now it's simple. Run the "Ipconfig /releasw" command to release it, and then run "Ipconfig /renew" to reconfigure it. The wonderful web pages are now in front of us again.
The second case failure: The MAC address of the proxy server corresponding to the ARP cache table of the client is incorrect
A very strange network failure occurred on several machines in the school: the machine could access other machines, but it could not access the address of the proxy server (i.e. the address of the gateway) 192.168.0.1, causing the machine to be unable to access the Internet.
Run the "Arp -a" command to check the current ARP item, but find that the MAC address corresponding to the host address 192.168.0.1 is 00-00-00-00-00-00-00, which is not the MAC address of the host at all! Run the "Arp -a 192.168.0.1 00-06-29-ee-08-bf" (correct MAC address) command, add an item in the ARP cache, associate the IP address with the correct physical address, and find that the fault is solved, the computer can ping the host and access the Internet normally.
We know that ARP (Address Reverse Protocol) is used to display or modify the physical address translation table of the Ethernet IP or token ring used. There is an ARP cache table in each computer with TCP/IP protocol installed. The IP address in the table corresponds to the MAC address one by one, while the mapping of the host's IP address to the MAC address always exists in the ARP cache table. However, due to some reasons of the system, the MAC address of the host in the ARP cache table cannot be updated and obtained, which causes the machine to be unable to access the Internet.