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The table below shows an example of an invalid class C addressing scheme.
Device
Device 1
Device 2
Device 3
Assuming the IP address for device 1 is valid, the IP address for device 2 is invalid because
the network identifier for each address must begin with 208.132.180.xxx. The IP
address for device 3 is invalid because it is using the same IP address as device 1.
The ping command can be used from a computer (see below) or from the web interface to
ensure that a device at an IP address is responding correctly.
Using the Ping Utility to Test Communications
Use the ping command to test communications between any two network devices. A ping
test may fail if an intervening firewall or device setting blocks such messages.
For example, follow these steps on a Windows computer:
1.
From the desktop, select Start > Run.
2.
The Run dialog box displays. In the Open field, enter ping nnn.nnn.nnn.nnn –t
(where
3.
Click OK or press the <Enter> key. A window opens showing a series of response
messages (explained below).
4.
To stop the ping utility, press <Ctrl+C> on the keyboard.
NOTE: The embedded web page includes a ping utility (see
page 55).
Response Messages
While running the ping utility, a series of response messages are displayed that are used to
determine the status of the communications link. For example, pinging a device with the
IP address 208.132.180.48 replies with a message similar to the following:
Reply from 208.132.180.48: bytes=32 time=2ms TTL=32
This is the correct response which indicates that the device at the specified address is
communicating correctly. The response time value may vary according to network traffic. If
one of the following messages are received:
•
Request timed out — There has been no response from the specified address.
Either the processor is not receiving data (from the computer) or is not sending data
back. Check that the device is powered on and set to the same address that was
pinged.
Also, check that the device is correctly connected to the network.
•
Reply from 208.132.180.48: Destination host unreachable — The IP
address of the computer is not in the same class as the device being pinged. Check
that the subnet mask on both the computer and the device are set to the same value.
Also check that both IP addresses are within the correct range for the chosen class and
are compatible (see
page 92 to select the subnet mask class that matches the IP address class).
IP Address
192.168.255.41
192.168.101.42
192.168.255.43
is the IP address of the device to test).
nnn.nnn.nnn.nnn
Subnet Mask
Subnet Mask
255.255.255.0
255.255.255.0
255.255.255.0
Diagnostic Tools
on page 91 and
Choosing an IP Address
SME 211 • Reference Information
on
on
93
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