Server Load balancer using NAT

Currently, F5 type dedicated server Load balancer is the most widely used Server Load balancer device in the data center. You may learn more about Server Load balancer by focusing on DNS technology. The DNS Server Load balancer technology mainly uses the round robin algorithm, but the DNS server load technology has a problem that is hard to solve: the client will buffer dns ip Address Resolution locally, so that subsequent applications will reach the same IP address. This is an acceleration technology, but it actually weakens the role of DNS load balancing technology. NAT Server Load balancer solves this problem. routers or other NAT devices translate multiple IP addresses that require load balancing into one public IP address (5) suppose we have a router with a serial interface and an Ethernet interface. The Ethernet port is connected to the internal network, and there are three WEB servers running the same WEB service on the internal network, the IP addresses are 2.2.2.1, 2.2.2.2, and 2.2.2.3 respectively, while 2.2.2.10 is the internal router port address (Ethernet Interface), and the external router port (Serial Interface) address is the Internet IP address, that is, the NAT Server Load balancer address is required. To handle a large number of WEB connection requests from the Internet, you need to configure NAT Server Load balancer on this vro, convert the packets sent to the valid Internet IP address of the WEB server to the internal local addresses of the three servers.

Assuming that the outer port address of the vro1.1.is 1.1.1.1, each TCP connection accessing 1.1.1.1 will be distributed to each backend Real WEB server according to the rules to achieve load balancing. The following figure uses Figure 5 as an example to briefly introduce the configuration process of NAT Server Load balancer on the vronat as follows:

Step 1: Define NAT on the vro interface.
Configure: ip nat inside & ip nat outside on the Interface
Step 2: Define a standard access list to identify the Internet IP address to be converted. Ip access-list 1 permit 1.1.1.1

Step 3: Create a server address pool. The following parameter uses rotary, indicating that we need to use the round robin (RoundRobin) method to retrieve the corresponding IP address from the NAT address pool to convert valid IP packets.
Ip nat pool websvr 2.2.2.1 2.2.2.3 netmask 255.255.255.0 type rotary

Step 4: Convert the destination IP address into the IP address defined in the address pool. So far, the NAT Server Load balancer settings have ended, isn't it easy?
Ip nat inside destination list 1 pool websvr

 

My personal summary: 1. experiment shows that load balancing can be achieved for WEB and FTP servers.
2. When a server fails, the client cannot open the service when it returns to the server. Turn it off and refresh it.
It seems that NAT Server Load balancer still has shortcomings ..
 

 

This article is from the "windows1009" blog