DNS Server Load balancer technology-a method that corresponds to multiple IP addresses for the same domain name

DNS load balancing technology is to configure multiple IP addresses for the same host name on the DNS server, the DNS server returns different resolution results for each query based on the IP address recorded by the host in the DNS file, and directs the client access to different machines, so that different clients can access different servers to achieve load balancing.

　　
The advantage of DNS load balancing is that it is cost-effective and simple, and the server can be anywhere on the Internet. However, it also has many disadvantages:
　　
In order to make the DNS server interact with other DNS servers in a timely manner, ensure that DNS data is updated in a timely manner, and enable random address allocation, the DNS refresh time is usually set to a small value, however, excessively small DNS traffic will increase, resulting in additional network problems.
　　
In the event of a server failure, even if the DNS settings are modified in time, it still takes enough time (refresh time) to take effect. During this period, the client computer that saves the address of the faulty server cannot access the server normally.
　　
DNS Server Load balancer uses a simple round-robin load algorithm, which does not distinguish between servers, does not reflect the current running status of servers, and cannot allocate more requests to servers with better performance, client Requests may even be concentrated on a server.
　　
Assign an Internet IP address to each server, which will occupy too many IP addresses.
The simplest way to determine whether a website uses DNS load balancing is to continuously ping the domain name. If the IP addresses returned by multiple DNS resolution are different, this site is likely to adopt a more common DNS load balancing. But not necessarily, because if DNS response balancing is used, the IP addresses returned for multiple resolutions may also be different. Ping www.yesky.com, www.sohu.com, and www.yahoo.com.
　　
Assume that there are three servers to respond to requests from www.test.com.
　　
The implementation under NT is also very simple. The following describes in detail the process of implementing DNS load balancing under Win2000 Server. NT4.0 is similar:
　　
Open "DNS" under "Administrative Tools" and go to the DNS service configuration console.
　　
Open the "attributes" of the corresponding DNS server, and select the "enable loop" check box in "server options" on the "advanced" tab. This step is equivalent to adding a dual-byte value (DWORD Value) roundrobin to the registry record HKEY_LOCAL_MACHINE/system/CurrentControlSet/services/DNS/parameters. The value is 1.
　　
Open the corresponding area (such as test.com) of the forward search area, and add host (a) resource records to the new host. The record is as follows:
　　
WWW in a 192.1.1.1
WWW in a 192.1.1.2
WWW in a 192.1.1.3
　　
The difference here is that the next host name in NT corresponds to multiple IP address records, but in UNIX, multiple different host names correspond to their own IP addresses first, then, these hosts are assigned the same alias (cname) for implementation.
　　
Note that the priority of the local subnet under NT will replace the reuse of multiple host names. Therefore, during testing, if the client IP Address used for testing is within the same mask range as the host resource record IP address, you need to clear "enable netmask sorting" in "advanced" tab "" server options ".