With source NAT, the inside local source address of an IP packet from a device in the internal
network is rewritten to an inside global address by a NAT device at the network transition.
With destination NAT, the inside global destination address of an IP packet from a device in
the external network is rewritten to an inside local address by a NAT device at the network
transition.
To translate the internal into the external IP address and back, the NAT device maintains a
translation list. The address assignment can be dynamic or static.
NAPT
In Network Address Port Translation (NAPT), several internal IP addresses are translated into
the same external IP address. To identify the individual nodes, the port of the internal device
is also stored in the translation list of the NAT device and translated for the external address.
If several internal devices send a query to the same external destination IP address via the
NAT device, the NAT device enters its own external source IP address in the header of these
forwarded frames. Since the forwarded frames have the same external source IP address, the
NAT device assigns the frames to the devices using a different port number.
If a device from the external network wants to use a service in the internal network, the
translation list for the static address assignment needs to be configured.
NAT/NAPT and IP routing
You can enable NAT/NAPT and IP routing at the same time. In this case, you need to regulate
the reachability of internal addresses from external networks with ACL rules.
9.1.1
The "show" commands
9.1.1.1
show ip nat config
Description
This command shows the global NAT/NAPT configuration.
Requirement
You are in the User EXEC mode or in the Privileged EXEC mode.
The command prompt is as follows:
cli>
or
cli#
Syntax
Call the command without parameter assignment:
show ip nat config
Layer 3 functions
9.1 NAT
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Configuration Manual, 07/2017, C79000-G8976-C361-06
