User manual

Publication 1734-UM011A-EN-P - February 2004
3-4 Configure the 1734-AENT Adapter for Your EtherNet/IP Network
When host B communicates with host A, it knows from A’s IP address that A
is on another network (the net IDs are different). In order to send data to A, B
must have the IP address of the gateway connecting the two networks. In this
example, the gateway’s IP address on Network 2 is 128.2.0.3.
The gateway has two IP addresses (128.1.0.2 and 128.2.0.3). The first must be
used by hosts on Network 1 and the second must be used by hosts on
Network 2. To be usable, a host’s gateway must be addressed using a net ID
matching its own.
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.
Take Network 2 (a Class B network) in the previous example and add another
physical network. Selecting the following subnet mask would add two
additional net ID bits, allowing for four physical networks:
11111111 11111111 11
000000 00000000 = 255.255.192.0
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 physical network.
EXAMPLE
These two bits of the Host ID used to
extend the net ID