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10.2 NAT
NAT can achieve Internet access by multiple hosts within the LAN through one or more public
network IP addresses. It means that few public network IP addresses represent more private network
IP addresses, thus saving public network IP addresses.
Private network IP address refers to the IP address of internal network or host, while public network
IP address is a globally unique IP address on the Internet.
RFC 1918 three IP address blocks for the private network as follows:
Class A: 10.0.0.0 ~ 10.255.255.255
Class B: 172.16.0.0~ 172.31.255.255
Class A: 192.168.0.0~ 192.168.255.255
The addresses within the above three ranges will not be allocated on the Internet. Therefore, they
can be freely used in companies or enterprises without the need to make application to the operator
or registration center
Page wizard: Firewall → NAT
Standard ACL can block all communication flows from a
network, or allow all communication flows from a particular
network, or deny all communication flows of a protocol stack
(e.g. IP) of.
The extended ACL provides a wider range of control than that
provided by the standard ACL. For example, if the network
administrator wants to "allow external Web communication
flows to pass through and reject external communication
flows, e.g. FTP and Telnet”, the extended ACL can be used to
achieve the objective. The standard ACL can not be controlled
so precisely.
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