GE GFK-1541B - Manual (Page 182)

GFK-1541B Chapter 6 Network Administration Support 6-7
6
Configuring Multiple Gateways
Multiple Gateways are supported on the Series 90-70 Ethernet Interface (Type 2) and the Series
90-30 CPU364 and CPU374 only.
An Ethernet Interface with the Multiple Gateways feature has the ability to route packets not only
through a single default gateway, but also through additional gateways located on the local
subnet.
The gateway that is configured in the Ethernet Interface’s hardware configuration (using the PLC
programming software) is defined as the default gateway. If supported in the Windows-based
PLC programming software, additional gateways can also be configured to define alternate routes
to remote subnets in the Routing tab of the Name Resolution and Routing Table Rack Operation.
One routing table may be defined for a PLC system, which is made available to all the Ethernet
Interfaces in that PLC.
Example: Configuring Multiple Gateways
This example is an extension of the example in Subnets and Multiple Gateways. Refer to that
example to understand how subnets are created and the subnet mask (255.255.192.0) was
determined. This example adds Subnet 2.3.
172.16.0.1
A
Network 1
172.17.64.1
B
172.17.64.2
C
172.17.64.3
G1
Local (Sub)Network 2.1
172.17.128.1
D
172.17.128.2
E
172.17.128.3
G2
(Sub)Network 2.2
172.16.0.2
Gateway
Gateway
172.17.64.4
172.17.192.1
F
172.17.192.2
H
172.17.192.3
G3
(Sub)Network 2.3
Gateway
172.17.64.5
A PLC on Network1, Subnet 2.2, and Subnet 2.3 can talk to a PLC on one of the other networks
without configuring multiple gateways because there is only one gateway on these networks.
Gateway G1 would be configured as the default gateway for PLC A’s Ethernet Interface;
Gateway G2 for PLC D’s and E’s Ethernet Interface; and Gateway G3 for PLC F’s and H’s
Ethernet Interface. The default gateway is configured in the Ethernet Interface’s module
configuration.
For Local Subnet 2.1, however, there are three gateways to choose from. The Ethernet Interfaces
in PLC B and C must decide where to send data in order for it to arrive at its destination. If you
have not configured these Ethernet Interfaces for multiple gateways and the data destination is not
on Local Subnet 2.1, then the only gateway option for each Ethernet Interface is the one you
configured as the default gateway in module configuration.