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9-2
Section
PING Command
164
9-1
Communications Testing Functions
The Ethernet Unit provides two functions that allow communications with other
node to be tested.
The PING command is a common way to perform echoback tests on Ethernet
networks. The PING command can be executed to see if nodes are physically
connected properly and to be sure that IP address are set for the correct Ether-
net nodes.
Echoback tests with specific nodes can also be performed by setting parameters
in the DM Area and then manipulating specific bits in memory. This type of inter-
node test can be performed only for remote nodes that support the FINS inter-
node testing function. Internode testing can be used to make sure settings for
FINS communications services are correct.
9-2
PING Command
The PING command sends an echo request packet to a remote node and re-
ceives an echo response packet to confirm that the remote node is communicat-
ing correctly. The PING command uses the ICMP echo request and responses.
The echo response packet is automatically returned by the ICMP.
The PING command is normally used to check the connections of remote nodes
when configuring a network. The Ethernet Unit supports both the ICMP echo re-
quest and reply functions.
If the remote node returns a normal response to the PING command, then the
nodes are physically connected correctly and Ethernet node settings are cor-
rect.
TCP
UDP
ICMP
IP
Ethernet
Echo request
Echo response
Remote Node
(host computer or Ethernet Unit)
Ethernet Unit
PC
9-2-1 Ethernet Unit
The Ethernet Unit automatically returns the echo response packet in response
to an echo request packet sent by another node (host computer or other Ether-
net Unit). An echo request packet can be sent to another node by issuing the
FINS command to execute the PING command from the PC. Refer to page 211
for details on the PING command.
9-2-2 Host Computer
The PING command can be executed from the host computer to send an echo
request packet to an Ethernet Unit. The method for using the PING command
from a UNIX computer is given next.
Method
Input the following at the host computer prompt ($):
$ ping
IP_address (host_name)
PING Command
Internode Testing