Configuration Guide Configuring NAT
No address pool is configured by default.
Use the ip nat pool address-pool start-address end-address { netmask mask | prefix-length prefix-length }
command to configure an IP address pool for NAT.
Configuring the ACL
No ACL is configured by default.
Use the access-list access-list-number permit ip-address wildcard command to configure a destination-based ACL.
Note that the ACL must be configured as an extended ACL based on destination IP address matching.
Configuring Inside Destination Address Translation
Inside destination address translation is not configured by default.
Use the ip nat inside destination list access-list-number pool address-pool command to configure inside
destination address translation. This configuration takes effect on TCP traffic only but not on other traffic, unless
additional NAT configuration has been performed.
10.3.5 Constructing a Local Server
A user has deployed three servers (an FTP server, a Web server, and an Email server) in an intranet, and hopes that
network hosts in a WAN can access the three servers while common users of the intranet can set the gateway as a device
to provide Internet access.
Working Principle
Map one or more internal hosts to a network server, so that users on the WAN obtain corresponding services from the
network server.
Related Configuration
Configuring NAT Interfaces
By default, no interfaces are NAT interfaces.
Run the ip nat { inside | outside } command to specify a couple of NAT interfaces.
NAT does not work on a data packet unless a route exists between the outside interface and the inside interface and
the data packet meets a certain rule. Therefore, at least one inside interface and one outside interface need to be
configured on the router.
Configuring Inside Address and Port Translation
Inside address and port translation is not configured by default.
Use the ip nat inside source static { udp | tcp } local-address port global-address port [ permit-inside ]
command to translate specific inside addresses and ports, so that corresponding services are provided on dedicated
ports. For example, TCP port 20 or 21 can be used to construct an FTP server, or TCP port 80 to construct a Web
server.
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