NAT_S615
Entry ID: 109744660, V1.1, 08/2017
Siemens AG All rights reserved
2.6 Cross communication for series machines with
NETMAP and destination NAT
Starting situation
In this case, several identical plant parts are to communicate among each other (in
this document: CPU2 to CPU1). All plant parts use the same subnet (in this
document: 192.168.2.x).
VLAN2: 192.168.1.0/24
VLAN1: 192.168.2.0/24
CPU1: 192.168.2.10
Gateway: 192.168.2.1
192.168.2.1
192.168.1.1
NAT Table
SRC IP:
192.168.1.3
DST IP:
192.168.1.2
SRC IP:
192.168.1.3
DST IP:
192.168.2.10
Addtl.IP:
192.168.1.2
CPU2: 192.168.2.10
Gateway: 192.168.2.1
192.168.2.1
192.168.1.10
NAT Table
SRC IP:
192.168.1.3
DST IP:
192.168.1.2
SRC IP:
192.168.2.10
DST IP:
192.168.1.2
Addtl.IP:
192.168.1.3
Prerequisite
A SCALANCE S615 is connected upstream to each plant part.
For network separation, the SCALANCE S615 has two VLANs with different
network IDs. As a result, the device has a separate IP address for each VLAN
(in this document: VLAN1: 192.168.2.1 and VLAN2: 192.168.1.1 or 192.168.1.10).
The SCALANCE S615 modules are connected via VLAN2.
This configuration requires NAT and cannot be solved with pure routing as the
subnet from VLAN1 could not be uniquely assigned, regardless of the direction of
connection establishment and gateways in the PC.
One SCALANCE S615 module is required for each identical internal subnet. It is
not possible to connect multiple identical subnets to a single SCALANCE S615.
Therefore, a NAT table is additionally defined in the SCALANCE S615 to translate
the PC’s message frames to a different IP address. This requires another IP
address from the subnet of VLAN2.
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