TCP/IP troubleshooting tools
The following list shows some of the TCP/IP diagnostic tools that
are included with Windows XP:
- Network Diagnostics in Help and Support
Contains detailed information about the network configuration
and the results of automated tests.
- Network Connections folder
Contains information and configuration for all network
connections on the computer. To locate the Network Connections folder, click
Start, click Control Panel, and then click
Network and Internet Connections.
- IPConfig command
Displays current TCP/IP network configuration values,
updates, or releases, Dynamic Host Configuration Protocol (DHCP) allocated
leases, and display, register, or flush Domain Name System (DNS)
- Ping command
Sends ICMP Echo Request messages to verify that TCP/IP is
configured correctly and that a TCP/IP host is available.
- Hostname command
Displays the name of the host computer.
- Nbtstat command
Displays the status of current NetBIOS over TCP/IP
connections, updates the NetBIOS name cache, and displays the registered names and
- PathPing command
Displays a path of a TCP/IP host and packet losses
at each router along the way.
- Route command
Displays the IP routing table and adds or deletes IP
- Tracert command
Displays the path of a TCP/IP host.
To view the correct command syntax to use with each of these
tools, type -?
at a command prompt after the name of the
Windows XP Professional tools
Windows XP Professional contains the following additional tools:
- Event viewer
Records system errors and events.
- Computer Management
Changes network interface drivers and other
The procedure that you use to troubleshoot TCP/IP issues depends
on the type of network connection that you are using and the connectivity
problem that you are experiencing.
For most issues that involve Internet connectivity, start by
using the Network Diagnostics tool to identify the source of the issue. To use
Network Diagnostics, follow these steps:
- Click Start, and then click Help
- Click the link to Use Tools to view your computer
information and diagnose problems, and then click Network
Diagnostics in the list on the left.
- When you click Scan your system, Network
Diagnostics gathers configuration information and performs automated
troubleshooting of the network connection.
- When the process is completed, look for any items that are marked
"FAILED" in red, expand those categories, and then view the additional details
about what the testing showed.
You can either use that information to resolve the issue or you
can provide the information to a network support professional for help. If you
compare the tests that failed with the documentation in the Manual
Troubleshooting section later in this article, you may be able to determine the
source of the issue. To interpret the results for TCP/IP, expand the Network
Adapters section of the results, and then expand the network adapter that
failed the testing.
You can also start the Network Diagnostics
interface directly by using the following command:
netsh diag gui
To manually troubleshoot your TCP/IP connectivity, use the
following methods in the order that they appear:
Method 1: Use the IPConfig tool to verify the configuration
To use the IPConfig tool to verify the TCP/IP
configuration on the computer that is experiencing the problem, click
, click Run
, and then type
. You can now use the ipconfig
command to determine the host computer configuration information,
including the IP address, the subnet mask, and the default
parameter for IPConfig generates a detailed configuration report
for all interfaces, including any remote access adapters. You can redirect
IPConfig output to a file to paste the output into other documents. To do this,
ipconfig > \folder_name\file_name
The output receives the specified file name and is stored in the
You can review the IPConfig output to identify
issues that exist in the computer network configuration. For example, if a
computer is manually configured with an IP address that duplicates an existing
IP address that is already detected, the subnet mask appears as
If your local IP address is returned as
with a subnet
mask of 255.255.0.0, the IP address was assigned by the Automatic Private IP
Addressing (APIPA) feature of Windows XP Professional. This assignment means
that TCP/IP is configured for automatic configuration, that no DHCP server was
found, and that no alternative configuration is specified. This configuration
has no default gateway for the interface.
If your local IP address is
returned as 0.0.0.0, the DHCP Media Sensing feature override turned on because
the network adapter detected its lack of connection to a network, or TCP/IP
detected an IP address that duplicates a manually configured IP
If you do not identify any issues in the TCP/IP
configuration, go to Method 2.
Method 2: Use the Ping tool to test your connectivity
If you do not identify any issues in the TCP/IP
configuration, determine whether the computer can connect to other host
computers on the TCP/IP network. To do this, use the Ping tool.
Ping tool helps you verify IP-level connectivity. The ping
command sends an ICMP Echo Request message to a destination host.
Use Ping whenever you want to verify that a host computer can send IP packets
to a destination host. You can also use Ping to isolate network hardware
problems and incompatible configurations.Note
If you ran the ipconfig /all
command, and the IP configuration appeared, you do not have to
ping the loopback address and your own IP address. IPConfig has already
performed these tasks to display the configuration. When you troubleshoot,
verify that a route exists between the local computer and a network host. To do
this, use the following command:
ping IP addressNoteIP address
is the IP address of the
network host that you want to connect to.
To use the ping
command, follow these steps:
- Ping the loopback address to verify that TCP/IP is
installed and correctly configured on the local computer. To do this, type the
ping 127.0.0.1 If the loopback test fails, the IP stack is not responding. This
problem may occur if any one or more of the following conditions is true:
- The TCP drivers are corrupted.
- The network adapter is not working.
- Another service is interfering with IP.
- Ping the IP address of the local computer to verify that
the computer was correctly added to the network. If the routing table is
correct, this procedure just forwards the packet to the loopback address of
127.0.0.1. To do this, type the following command:
ping IP address of local host If the loopback test succeeds but you cannot ping the local IP
address, there may be an issue with the routing table or with the network
- Ping the IP address of the default gateway to verify that
the default gateway is working and that you can communicate with a local host
on the local network. To do this, type the following command:
ping IP address of default gateway If the ping fails, you may have an issue with the network
adapter, the router or gateway device, the cabling, or other connectivity
- Ping the IP address of a remote host to verify that you can
communicate through a router. To do this, type the following command:
ping IP address of remote host If the ping fails, the remote host may not be responding, or
there may be a problem with the network hardware between computers. To rule out
an unresponsive remote host, use Ping again to a different remote
- Ping the host name of a remote host to verify that you can
resolve a remote host name. To do this, type the following command:
ping Host name of remote host Ping uses name resolution to resolve a computer name into an IP
address. Therefore, if you successfully ping an IP address but you cannot ping a
computer name, there is a problem with host name resolution, not with network
connectivity. Verify that DNS server addresses are configured for the computer,
either manually in the properties of TCP/IP, or by automatic assignment. If DNS
server addresses are listed when you type the ipconfig /all command, try to ping the server addresses to make sure that they
If you cannot use Ping successfully at any point, verify the
- Make sure that the local computer's IP address is valid and
that it is correct on the General tab of the Internet
Protocol (TCP/IP) Properties dialog box or when it is used with the
- Make sure that a default gateway is configured and that the
link between the host and the default gateway is working. For troubleshooting
purposes, make sure that only one default gateway is configured. Although you
can configure more than one default gateway, gateways after the first gateway
are used only if the IP stack determines that the original gateway is not
working. The purpose of troubleshooting is to determine the status of the first
configured gateway. Therefore, you can delete all the other gateways to
simplify your task.
- Make sure that Internet Protocol security (IPSec) is not
turned on. Depending on the IPSec policy, Ping packets may be blocked or may
require security. For more information about IPSec, go to Method 7: Verify
Internet Protocol security (IPSec).
If the remote computer that you are pinging is across a
high-delay link such as a satellite link, response may take longer. You can use
(wait) parameter to specify a longer timeout period than the
default timeout of four seconds.
Method 3: Use the PathPing tool to verify a route
The PathPing tool detects packet loss over multiple-hop
paths. Run a PathPing analysis to a remote host to verify that the routers on
the way to the destination are operating correctly. To do this, type the
pathping IP address of remote host
Method 4: Use the Arp tool to clear the ARP cache
If you can ping both the loopback address (127.0.0.1)
and your IP address but you cannot ping any other IP addresses, use the Arp tool to
clear out the Address Resolution Protocol (ARP) cache. To view the cache
entries, type any one of the following commands:
To delete the entries, type the following command:
arp -d IP address
To flush the ARP cache, type the following command:
netsh interface ip delete arpcache
Method 5: Verify the default gateway
The gateway address must be on the same network as the
local host. Otherwise, messages from the host computer cannot be forwarded
outside the local network. If the gateway address is on the same network as the
local host, make sure that the default gateway address is correct. Make sure
that the default gateway is a router, not just a host. And make sure that the
router is enabled to forward IP datagrams.
Method 6: Use the Tracert tool or the Route tool to verify communications
If the default gateway responds correctly, ping a
remote host to make sure that network-to-network communications are working
correctly. If communications are not working correctly, use the Tracert tool to
trace the path of the destination. For IP routers that are Microsoft Windows
2000-based or Microsoft Windows NT 4.0-based computers, use the Route tool or
the Routing and Remote Access snap-in to view the IP routing table. For other
IP routers, use the vendor-designated appropriate tool or facility to examine
the IP routing table.
Most frequently, you receive the following four
error messages when you use Ping during troubleshooting:
This error message means that the number of
required hops exceeds the Time to Live (TTL). To increase TTL, by use the ping -i
command. A routing loop may exist. Use the Tracert
command to determine whether misconfigured routers have caused a
Destination Host Unreachable
This error message means that no local or remote route exists for a destination
host at the sending host or at a router. Troubleshoot the local host or the
router's routing table.
This error message means that the Echo Reply messages were not received in the
designated timeout period. By default, the designated timeout period is four
seconds. Use the ping -w
command to increase the timeout.
request could not find host
This error message means that the
destination host name cannot be resolved. Verify the name and the availability
of DNS or WINS servers.
Method 7: Verify Internet Protocol security (Ipsec)
IPSec can improve security on a network, but changing network configurations or troubleshooting
problems more difficult. Sometimes, IPSec policies require secured communication on a Windows
XP Professional-based computer. These requirements can make it difficult to
connect to a remote host. If IPSec is implemented locally, you can turn off the
IPSEC Services service in the Services snap-in.
If the difficulties
end when you stop the IPSec services, IPSec policies are either blocking the
traffic or requiring security for the traffic. Ask the security administrator
to modify the IPSec policy.
Method 8: Verify packet filtering
Because of mistakes in packet filtering, address
resolution or connectivity may not work. To determine whether packet filtering
is the source of a network problem, turn off TCP/IP packet filtering. To do
this, follow these steps:
- Click Start, click Control
Panel, click Network and Internet Connections, and
then click Network Connections.
- Right-click the local area connection that you want to
modify, and then click Properties.
- On the General tab, in the This
connection uses the following items list, click Internet
Protocol (TCP/IP), and then click
- Click Advanced, and then click the
- In the Optional Settings dialog box, click
TCP/IP Filtering, and then click the
- Click to clear the Enable TCP/IP Filtering (All
adapters) check box, and then click OK.
To ping an address, use its DNS name, its NetBIOS computer
name, or its IP address. If the ping succeeds, the packet filtering options may
be misconfigured or too restrictive. For example, the filtering can allow the
computer to act as a Web server, but, to do this, the filtering may turn off tools such as
remote administration. To restore a wider range of permissible
filtering options, change the permitted values for the TCP port, the UDP port,
and the IP protocol.
Method 9: Verify the connection to a specific server
To determine the cause of connectivity problems when
you are trying to connect to a specific server through NetBIOS-based
connections, use the nbtstat -n
command on the server to determine what name the server
registered on the network.
The nbtstat -n output
command lists several names that the computer has registered. The
list will include a name that looks similar to the computer's name that is
configured on the Computer Name
in Control Panel. If not, try one of the other unique
names that the nbtstat
The Nbtstat tool can also display the
cached entries for remote computers from #PRE entries in the Lmhosts file or
from recently resolved names. If the name that the remote computers are using
for the server is the same, and the other computers are on a remote subnet,
make sure that the other computers have the computer's name-to-address mapping
in their Lmhosts files or WINS servers.
Method 10: Verify remote connections
To determine why a TCP/IP connection to a remote
computer stops responding, use the netstat -a
command to show the status of all activity for TCP and UDP ports
on the local computer.
Typically, a good TCP connection shows 0 bytes
in the Sent
queues. If data is
blocked in either queue or the state of the queues is irregular, the connection
may be faulty. If data is not blocked, and the state of the queues is typical,
you may be experiencing network or program delay.
Method 11: Use the Route tool to examine the routing table
For two hosts to exchange IP datagrams, both hosts must
have a route to each other, or they must use default gateways that have a route. To
view the routing table on a Windows XP-based host, type the following command:
Method 12: Use the Tracert tool to examine paths
Tracert sends ICMP Echo Request messages that have
incrementally higher values in the IP header TTL field to determine the path
from one host to another through a network. Then Tracert analyzes the ICMP
messages that are returned. With Tracert, you can track the path from router to
router for up to 30 hops. If a router has failed, or the packet is routed into
a loop, Tracert reveals the problem. After you locate the problem router, you
can contact the router administrator if the router is offsite, or you can
restore the router to fully functional status if the router is under your
Method 13: Troubleshoot gateways
If you receive the following error message during
configuration, determine whether the default gateway is located on the same
logical network as the computer's network adapter:
default gateway does not belong to one of the configured interfaces
Compare the network ID part of the default gateway IP address with the network
IDs of the computer's network adapters. Specifically, verify that the bitwise
of the IP address and the subnet mask equals the bitwise logical AND
of the default gateway and the subnet mask.
example, a computer that has a single network adapter that is configured with
an IP address of 172.16.27.139 and a subnet mask of 255.255.0.0 must use a
default gateway of the form
. The network
ID for this IP interface is 172.16.0.0.
The following resources contain additional information about how
to troubleshoot Microsoft TCP/IP:
See the "Configuring TCP/IP" topic in the
documentation for the Microsoft Windows XP Professional Resource
See "Introduction to TCP/IP" in the TCP/IP Core Networking Guide
of the Microsoft Windows 2000 Server Resource Kit for general
information about the TCP/IP protocol suite.
See "Unicast Routing
Overview" in the Internetworking Guide
of the Microsoft Windows 2000 Server Resource Kit for more
information about routing principles.
See "TCP/IP Troubleshooting" in the TCP/IP Core Networking Guide
of the Microsoft Windows 2000 Server Resource Kit for more
information about IP packet filtering.