Basic network troubleshooting.

Cause:
If a computer is unable to connect to a network or see other computers
on a network, it may be necessary to troubleshoot the network. A
network may not work because of any of the below reasons.

Network card not connected properly.
Bad network card drivers or software settings.
Firewall preventing computers from seeing each other.
Connection related issues.
Bad network hardware.
Solution:

Because of the large variety of network configurations, operating
systems, setup, etc... not all of the below information may apply to
your network or operating system. If your computer is connected to a
company or large network, or you are not the administrator of the
network, it is recommended that if you are unable to resolve your
issues after following the below recommendations that you contact the
network administrator or company representative.

Note: If you are being prompted for a Network password and do not know
the password, Computer Hope is unable to assist users with obtaining a
new or finding out the old password.

VERIFY CONNECTIONS / LEDs

Verify that the network cable is properly connected to the back of the
computer. In addition, when checking the connection of the network
cable, ensure that the LEDs on the network are properly illuminated.
For example, a network card with a solid green LED or light usually
indicates that the card is either connected or receiving a signal.
Note: generally, when the green light is flashing, this is an
indication of data being sent or received.

If, however, the card does not have any lights or has orange or red
lights, it is possible that either the card is bad, the card is not
connected properly, or that the card is not receiving a signal from the
network.

If you are on a small or local network and have the capability of
checking a hub or switch, verify that the cables are properly connected
and that the hub or switch has power.

ADAPTER RESOURCES

Ensure that if this is a new network card being installed into the
computer that the card's resources are properly set and/or are not
conflicting with any hardware in the computer.

Users who are using Windows 95, 98, ME, 2000 or XP, verify that device
manager has no conflicts or errors. Additional help and information
about device manager and resources can be found on our device manager
page.

ADAPTER FUNCTIONALITY

Verify that the network card is capable of pinging or seeing itself by
using the ping command. Windows / MS-DOS users ping the computer from a
MS-DOS prompt. UNIX / Linux variant users ping the computer from the
shell.

To ping the card or the localhost, type either

ping 127.0.0.1

or

ping localhost

This should show a listing of replies from the network card. If you
receive an error or if the transmission failed, it is likely that
either the network card is not physically installed into the computer
correctly, or that the card is bad.

PROTOCOL

Verify that the correct protocols are installed on the computer. Most
networks today will utilize TCP/IP, but may also utilize or require
IPX/SPX and NetBEUI.

Additional information and help with installing and reinstalling a
network protocol can be found on document CH000470.

When the TCP/IP protocol is installed, unless a DNS server or other
computer assigns the IPX address, the user must specify an IP address
as well as a Subnet Mask. To do this, follow the below instructions.

Click Start / Settings / Control Panel

Double-click the Network icon

Within the configuration tab double-click the TCP/IP protocol icon.
Note: Do not click on the PPP or Dial-Up adapter, click on the network
card adapter.

In the TCP/IP properties click the IP address tab

Select the option to specify an IP address

Enter the IP address and Subnet Mask address, an example of such an
address could be:

IP Address: 102.55.92.1
Subnet Mask: 255.255.255.192

When specifying these values, the computers on the network must all
have the same Subnet Mask and have a different IP Address. For example,
when using the above values on one computer you would want to use an IP
address of 102.55.92.2 on another computer and then specify the same
Subnet Mask.

FIREWALL

If your computer network utilizes a firewall, ensure that all ports
required are open. If possible, close the firewall software program or
disconnect the computer from the firewall to ensure it is not causing
the problem.

ADDITIONAL TIME

In some cases it may take a computer some additional time to detect or
see the network. If after booting the computer you are unable to see
the network, give the computer 2-3 minutes to detect the network.
Windows users may also want to try pressing the F5 (refresh) key when
in Network Neighborhood to refresh the network connections and possibly
detect the network.

ADDITIONAL TROUBLESHOOTING

If after following or verifying the above recommendations you are still
unable to connect or see the network, attempt one or more of the below
recommendations.

If you have installed or are using TCP/IP as your protocol you can
attempt to ping another computer's IP address to verify if the computer
is able to send and receive data. To do this, Windows or MS-DOS users
must be at a prompt and Linux / UNIX variant users must open or be at a
shell.

Once at the prompt assuming, that the address of the computer you wish
to attempt to ping is 102.55.92.2, you would type:

ping 102.55.92.2

If you receive a response back from this address (and it is a different
computer), this demonstrates that the computer is communicating over
the network. If you are still unable to connect or see the network, it
is possible that other issues may be present.

Another method of determining network issues is to use the tracert
command if you are a MS-DOS or Windows user or the traceroute command
if you are a Linux / UNIX variant user. To use this command you must be
at the command prompt or shell.

Once at the prompt, assuming that the address is again 102.55.92.2,
type:

tracert 102.55.92.2

or

traceroute 102.55.92.2

This should begin listing the hops between the computer and network
devices. When the connection fails, determine which device is causing
the issue by reviewing the traceroute listing.