Network Address Translation (NAT) is one of the most widely used features in Internet cafes, designed to solve the problem of insufficient IP addresses. Typically, an ISP provides only a single IP address to an Internet cafe, yet there are a large number of PCs inside the cafe. How can all these PCs access the Internet through this one unique IP address?
The answer is NAT, or Internet cafe network IP address translation.
When an internal PC accesses the external network, a corresponding entry is created inside the Internet cafe router. This entry contains information such as the internal PC, IP address, the external IP address being accessed, internal IP port, access destination, IP port, and so on. Therefore, every ping, QQ session, download, or web visit establishes a corresponding relationship entry on the router. If there is data communication on the network connection corresponding to that entry, these entries are retained in the Internet cafe router. If there is no data communication, it takes 20 to 150 seconds for them to disappear. For the RG-NBR series routers, these times are configurable.
Currently, there are several types of network viruses that, in a very short period, send out tens of thousands of consecutive connection requests targeting different IPs. This forces the Internet cafe router to establish tens of thousands of NAT connections for that one PC.
Since the number of NAT connections on an Internet cafe router is limited, if all of them are consumed by these viruses, other users trying to access the network will be unable to do so because there are no NAT connection resources left. This results in a network disconnection, which is actually caused by network viruses occupying all the NAT resources.
To address this situation, many Internet cafe routers offer a feature that allows setting the maximum number of NAT connections for internal PCs