Rockwell Automation 1732E-OB8M8SR EtherNet/IP Dual Port 8-Point SOE Input and Scheduled Output Modules UM - Manual (Page 36)

26 Rockwell Automation Publication 1732E-UM003B-EN-E - March 2014
Chapter 5 Configure the Module for Your EtherNet/IP Network
Subnet Mask
The subnet mask is used for splitting IP networks into a series of subgroups, or
subnets. The mask is a binary pattern that is matched up with the IP address to
turn part of the Host ID address field into a field for subnets.
Two bits of the Class B host ID have been used to extend the net ID. Each unique
combination of bits in the part of the Host ID where subnet mask bits are 1
specifies a different logical network.
The new configuration is:
A second network with Hosts D and E was added. Gateway G2 connects
Network 2.1 with Network 2.2.
Hosts D and E use Gateway G2 to communicate with hosts not on Network 2.2.
Hosts B and C use Gateway G to communicate with hosts not on Network 2.1.
When B is communicating with D, G (the configured gateway for B) routes the
data from B to D through G2.
EXAMPLE Take Network 2 (a Class B network) in the previous
example and add another network. Selecting the following
subnet mask would add two additional net ID bits, allowing
for four logical networks:
1111111 11111111 11000000 00000001 = 255.255.192.0
These two bits of the host ID used to
extend the net ID
Network 1
Network 2.1
Network 2.2
128.1.0.1
128.1.0.2
128.2.128.3
A
B C
G
D E
G2
128.2.64.3
128.2.128.2 128.2.128.1
128.2.64.1