NAT (network address translation) simply translates an IP address into another IP address, which is typically used for conversion between unregistered internal addresses and legitimate, registered Internet IP addresses. It is suitable for resolving the Internet IP address tension, do not want to let the network outside know the internal network structure and so on. Each NAT conversion is bound to increase the cost of the NAT device, but this extra overhead is trivial for most networks, except on networks with high bandwidth and large NAT requests.
NAT Load Balancer maps an external IP address to multiple internal IP addresses, dynamically converting each connection request to an internal server address, and connecting the external connection request to the server where the address is converted, thus achieving load balancing purposes.
Nat load Balancing is a more perfect load balancing technology, the device that plays NAT load balancing function is in the gateway location between internal server and external network, such as router, firewall, four layer switch, special load balancer, etc., the equalization algorithm is also more flexible, such as random selection, Minimum number of connections and response time to distribute the load. NAT load Balancing can be implemented by means of hardware and software. A device that implements NAT load balancing by software is often limited by bandwidth and the ability of the system itself to handle it, and because Nat is closer to the lower level of the network, it can be integrated into a hardware device, typically a layer fourth switch and a dedicated load balancer. One of the key features of layer fourth switches is NAT load balancing. The following example describes the configuration of Cisco router NAT load Balancing:
There is a router with a serial interface and a Ethernet interface, the Ethernet port is connected to the internal network, there are three Web servers on the internal network, but all are only low-end configuration, in order to handle a large number of Web connection requests from the Internet, It is therefore necessary to do a NAT load balancing configuration on this router to convert the messages sent to the legitimate Internet IP address of the Web server into the internal local addresses of the three servers. The specific configuration process is as follows:
1. Do the basic configuration of the router and define whether the interfaces are internal or external when NAT is done. 2. Then define a standard access list to identify the legitimate IP to convert
Address. 3. Define the NAT address pool to identify the local address of the internal Web server, and note the use of the keyword
Rotary, which indicates that we want to use round robin (Round Robin) to remove the corresponding IP address from the NAT address pool to convert legitimate IP packets. 4. Finally, the destination address is converted to the IP address in the address pool as defined in the Access table. The corresponding configuration file is as follows:
Interface ethernet0/0
IP address 192.168.1.4 255.255.255.248 IP nat inside
!
Interface serial0/0
IP address 200.200.1.1 255.255.255.248 IP nat outside!
IP access-list 1 Permit 200.200.1.2!
IP nat Pool websrv 192.168.1.1 192.168.1.3 netmask 255.255.255.248 type rotary IP nat inside destination List 1 pool webs Rv
