Anti-attack ability of firewall
——As a kind of security protection equipment, network security firewall，the firewall is naturally the target of many attackers in the network, so the anti-attack ability is also a necessary function of the firewall

NAT technology
——NAT technology can transparently translate all internal addresses, so that the external network cannot understand the internal structure of the internal network. At the same time, the connection with the external network can only be initiated by the internal network, which greatly improves the internal network safety.

-Another obvious use of NAT is to solve the problem of lack of IP addresses.

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