Chapter 5. CommunicationsGFK-2222AD April 2018 183The following examples would be problematic:Problem example #1:Figure 45: CPE330 Overlapping Local IP Subnet ExampleThe issue demonstrated in Figure 45 is that requests entering one CPE330 interface can be routed outthe other interface since both CPE330 Ethernet ports have been configured to be on the same network(255.255.0.0) but are physically connected to separate networks. Avoid this by assigning non-overlappingSubnets.Problem example #2:A user wishes to communicate through a routed network to an RX3i CPU with multiple networkinterfaces (CPE330, in this example). This remote IP device is configured with the following IP parameters:IP 192.168.0.5Subnet Mask 255.255.255.0Gateway 192.168.0.250LAN1 and LAN2 on the CPE330 are initially configured with following problematic IP parameters:LAN1 LAN2IP 10.10.0.1 192.168.0.1Subnet Mask 255.255.255.0 255.255.255.0Gateway 10.10.0.249 0.0.0.0The user intends to communicate between the remote device and CPE330 LAN1 (Figure 46). IP Addressrouting allows the CPE330 to receive the remote IP requests through the respective gateways(192.168.0.250 for the remote node and 10.10.0.249 for CPE330 LAN1). However, since CPE330 LAN2shares the same IP subnet as the remote network (192.168.0.x), responses may be routed to the local192.168.0.x network rather than to the remote network (Figure 47).The duplicate IP subnet in the example must be eliminated. One way to do this is simply change the IPAddress assigned to CPE330 LAN2 from 192.168.0.1 to 192.168.1.1 thereby creating a non-overlapping192.168.1.x network. In short, consider the totality of the network when assigning IP subnets and IPAddresses.
