Siemens SCALANCE XM-400 Configuration Manual page 69

itself count as "Outside" for this interface. All networks reachable via other IP interfaces of the
same device count as "Inside" for the NAT interface.
If there s routing via the NAT interface, the source or destination IP addresses of the transferred
data packets are changed at the transition between "Inside" and "Outside". Whether or not the
source or destination IP address is changed depends on the communications direction. It is
always the IP address of the communications node that is located "Inside" that is adapted.
Depending on the perspective the IP address of a communications node is always designated
as "Local" or "Global".
Position
Example
In the example two IP subnets are connected together via an IE switch. The division is from
the perspective of the NAT interface 10.0.0.155. The communication of PC2 with PC1 is
implemented via NAT/NAPT.
The actual IP address of PC1 (inside local) is implemented statically with NAT. For PC2, PC1
can be reached at the inside global address.
Position
SCALANCE XM-400/XR-500 Web Based Management (WBM)
Configuration Manual, 05/2017, C79000-G8976-C248-12
Local
Inside An actual IP address that is as‐
signed to a device in the internal
network. This address cannot be
reached from the external network.
Outside An actual IP address that is assigned to a device in the external network.
Since only "Inside" addresses are converted, there is no distinction
made between outside local and outside global.
VLAN X: 192.168.16.0/24
Local
Inside 192.168.16.150
Outside 10.0.0.10
Technical basics
4.9 NAT/NAPT
Perspective
Global
An IP address at which an internal
device can be reached from the
external network.
VLAN Y: 10.0.0.0/24
Perspective
Global
10.0.0.7
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