Layer 3 functions
9.9 NAT (IPv4)
SCALANCE XM-400/XR-500 Command Line Interface (CLI)
Configuration Manual, 06/2016, C79000-G8976-C252-11
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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.
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.
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.
The "show" commands
9.9.1.1
show ip nat config
Description
This command shows the global NAT/NAPT configuration.
You are in the User EXEC mode or in the Privileged EXEC mode.
The command prompt is as follows:
cli> or cli#
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