Set up IP address conflicts caused by Network Bridge and ICS at the same time

Failure phenomenon

There are 4 machines on the network: two Windows XP and two Windows 98 make up a Peer-to-peer network through a hub connection. And through one of the Windows XP machines through ADSL sharing Internet access (through Windows XP Bridge function), the previous period has been running well.

Two days ago, the machine directly connected to the Internet did not see any other machines in the "Network Neighborhood" and was found to be in conflict with other machine IP addresses by checking for 192.168.0.1. It can't be changed in any way! After using the Ipscan software check, another Windows XP machine was found to occupy two IP addresses ( 192.168.0.1 and 192.168.0.15, where 192.168.0.15 is my set, hostname is the name of another machine! But this computer has only one network card: Use ipconfig check also has only one network card use 192.168.0.15 address. Right now. If you unplug the network cable and then plug in the network cable or the first screen connected to the hub network and then enable the Internet, it can be all the same as normal.

Diagnostics process

Why does the computer automatically get an 192.168.0.1 address? Under what circumstances will the computer be able to move its 192.168.o.1 address? First, there is a DHCP server in the network, which is dynamically assigned IP address by the DHCP server for the computers within the network; The IP address pool range for the DHCP server is 192.168.0.1~192.168.0.254.

As it stands, there is certainly no and no need for a dedicated DHCP server to be a Peer-to-peer network with only 4 computers. Who else would provide the DHCP service? Naturally, I thought of the Windows ICS service.

Internet Connection Sharing (ICS) connects multiple computers to inernet using an Internet connection. A computer called the ICS host connects directly to the Internet and then shares its connections with the rest of the computers on the network. Client computers rely on the ICS host computer to provide access to the Internet. Enabling ICS can enhance security: Because only the ICS host computer is visible to the Internet. All communications from the client computer to the Internet are passed through the ICS host computer, which hides the address of the client computer from the Internet and is protected because the client computer cannot be seen from outside the network. Only computers running ICS are seen from the public side. Additionally, the ICS host computer manages network addressing. The ICS host computer assigns a permanent address to itself, while providing each ICS client with a Dynamic Host Configuration Protocol DHCP for which it assigns a unique address, which provides a way for computers on the network to communicate with each other.

Very simply, this computer is set up as an ICS host. The Internet Connection Sharing host itself has a DHCP service that sets the local computer's LAN port to 192.168.0.1 and automatically assigns IP addresses dynamically to other computers within the network, which are 192.168.2~192.l68.254. So, after the computer starts: it assigns itself an IP address. You can then assign an IP address to a computer that does not have an IP address, which enables network connectivity and Internet sharing.

Therefore, after setting up the ICS host computer within the network: All computers are not assigned IP addresses. The reasons are as follows:

Second, when the ICS host computer is powered on: All computers will automatically obtain an IP address from the ICF host for communication;

Second, if the ICS host computer is not powered on, the Windows computer automatically assigns a private IP address to the machine using APIPA (Automatic private IP addressing, Automatic Private IP addressing). This address is from the reserved authorized private address segment 169.254.0.1,169.254.255.254, which has a subnet mask of: 255.255.0.0. The computer is still able to communicate normally.

Therefore, the second NIC of ICS, and all computers within the network, do not set IP addresses, and all computers are set up to automatically obtain an IP address. Of course, with the ADSL m0dem connection of the network card must be set up IP address Oh, need it to connect with the Internet. In other words, the entire network, only with the Internet connection to the network card to set the IP address, all other network adapters do not need to set IP address.

It was found that the computer that was the Internet connection server set up both a bridge and an Internet connection share, removing the network bridge: only Internet Connection Sharing is maintained and the network is back to normal.

Excluding experience

There can only be one network administrator within the network, otherwise, everyone to the server to set up, it is very easy to cause the failure of network services, and failure to check and eliminate will also be very difficult: because usually, as ordinary computer users, it is difficult to know where to start, often in the last resort, reinstall the server.