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TCPIP Problem Solving
Address and Name Resolution
NetBIOS Problem Solving
Utilities to Troubleshoot Connectivity Problems


TCPIP Problem Solving     Top

1.  Click Start | Run then type winipcfg /all in Windows 9x, 
     or ipconfig /all at a Windows NT/2000/XP command prompt to display your 
     TCP/IP configuration.  Check to make sure your IP address, 
     subnet mask and default gateway are correct. 
     Additionally, if your network uses WINS or DNS, check to see that
     those server addresses are correct.  
     If your configuration is incorrect, you can modify it in Network properties. 

2.  Next, use Ping to test IP connectivity:

     Ping the loopback address of the host having a problem.  This will verify
     that TCP/IP is installed and configured properly on the computer.
     ping or ping loopback

Ping the IP address of the local computer.  This will verify that it was
     added to the network correctly.
     ping IP_address_of _local_computer

     Ping the IP address of the default gateway (router).  This will verify the
     router is working and you can communicate with a host on the local network.
     ping IP_address_of _default_gateway

Ping the IP address of remote host.  This will verify you can communicate
     through the router..
     ping IP_address_of _remote_host

3.  If any of these Ping tests fail

check :
Is the TCP/IP protocol installed on the computer?  Check the 
TCP/IP configuration.  Is it correct?  Does your network
use static IP addresses or dynamically assigned addresses (DHCP)?
Is your network card listed correctly in Network properties?
Do you have the latest driver for your network card?
If the first 2 Ping tests pass, but the third test fails, you may have an 
infrastructure problem.  An infrastructure problem could involve
cabling and/or the hub or switch your computer is attached to. 
Also, the router may be down or not configured properly.
If the first 3 Ping tests pass, but not the fourth, then you most likely have a router configuration problem.  Try to ping several known good remote hosts.  If they all don't respond, look to the router for the problem.          Top

Address and Name Resolution

If you are able to Ping a host using  the Host's IP address, but cannot Ping 
the host using it's name, then you have a Name Resolution Problem.

ping - works
ping server1 - doesn't work

Host names are resolved to IP address depending on what type of application
interface is used.  There are 2 types, TCP/IP sockets names and NetBIOS names.
Sockets applications include Ping, FTP, Telnet, WWW.  NetBIOS applications
would be net use, net view, and connecting to resources through Network Neighborhood.

The following table shows how these names are resolved to IP address:

Sockets  Names NetBIOS Names
local hostname  local hostname
then HOSTS file netbios cache first
then DNS then WINS 
then netbios cache then Broadcast
then WINS then LMHOSTS file
then Broadcast  then HOSTS file
and finally LMHOSTS file and finally DNS

In order to use WINS and/or DNS, there must be a WINS and/or DNS server 
on your network, and your TCP/IP properties must be configured with these 
server's IP addresses.

In order to use a HOSTS or LMHOSTS file, these files must be created
and added to the computer.

NetBIOS Problem Solving

1.  When troubleshooting name resolution issues, it is important to narrow down 
     whether the application is resolving a NetBIOS name or a sockets name.

2.  Once this is decided, you can look at the table above to see what your 
     computer is configured for as far as name resolution.  Do you have a
     WINS server added to your TCP/IP configuration, or a DNS server?
     If not, do you have a LMHOSTS or HOSTS file.

3.  If you do have the proper name resolution resource, but are still unable to
     resolve names to IP address, then look to that resource as the fault point.
     - Verify the IP addresses of the WINS and/or DNS servers.
     - Open the HOSTS and/or LMHOSTS files to see if the device you are 
       trying to resolve is added.
     - Ping the DNS or WINS server to make sure it is actually there.
     - Finally, if you have the proper resource configured, it is on the network
       (for example a DNS server), but you still cannot resolve names, then it's
       possible the resource (DNS server) is not configured properly.  

Utilities to Troubleshoot Connectivity Problems     Top

There are several Windows utilities you can employ to help resolve network
connectivity problems.  The following table lists some (but not all) of these

Utility Description Example
ping tcp/ip utility to verify a host exits.  ping
ping myserver1
tracert utility to trace the route of a packet from
router to router until it reaches it's destination.
tracert myserver1
arp view and modify arp table entries on a local
computer.  shows ip addresses to MAC addresses.
arp -a
arp -g

shows the arp cache
nbtstat view and modify the NetBIOS name cache.
can be used to get the MAC address of any
Windows computer.
nbtstat -c
shows the NetBIOS cache
including IP addresses

nbtstat -a <name>
<name> is a computer name

shows NetBIOS cache of <name> and that computer's MAC address
netstat displays current TCP/IP connections.  can be 
used to see if an intruder is connected to your PC
through a TCP or UDP port.
netstat -a 
shows all TCP/IP connections

netstat -r
shows all TCP/IP connections plus the local routing table
ipconfig shows TCP/IP configuration on a Windows NT
shows partial IP configuration info

ipconfig /all
shows all IP configuration info
winipcfg shows TCP/IP configuration on a Windows 9x
shows partial IP configuration info

winipcfg /all
shows all IP configuration info


The above utilities are run in a DOS window or at a command prompt.
winipcfg can also be run from Start | Run.
To see more information about each utility, type the utility name plus /?.
example:  netstat /? or arp /? (notice the space)

For more information about TCP/IP and NetBIOS issues check the Windows
Resource Kits, or you can search the Microsoft Knowledgebase: