Windows

Windows XP Help

Resolving Network issues

1. Tools to resolve network issues

To resolve network issues there are a number of free tools you can use to resolve the problem:
a) Windows Network Diagnostics. See Network Connections for link to Diagnose and Repair network issues. You might be
able to launch it from Help and Support as well.

b) IPCONFIG. Used to display or renew IP configurations.

c) PING. To send ICMP packets between computers to test if a computer responds. It can also do simple DNS resolution as well
using the -a parameter.

d) NSLOOKUP. Used to resolve DNS issues.

e) NETSTAT. Used to display network statistics such as connections, bytes sent/received, routing table, ports and programs.

2. Testing your network card. Use the following steps to check your card.

a) Type IPCONFIG /ALL on a command prompt. You should have an IP address (IPv4), a Default Gateway (also known as router),
a Netmask, one or more DNS addresses and in some cases one or more WINS addresses.
b) If your IP address starts with 10.x.x.x or 172.x.x.x or 192.168.x.x then you have a Private IP Address which can be routed though
to the internet via a Router that supports NAT (Network Address Translation) into a Public IP Address which is dynamically allocated by
your ISP. Other addresses are Public IP addresses which are allocated directly by your ISP.
c) If your IP address is 0.0.0.0 or 169.254.x.x then you either do not have an IP address or you have been allocation an APIPA (Auto
Private IP Addressing) address which cannot be used to access the Internet. Check to see if DHCP is enabled, configured and working from your
router or modem.
d) Type PING 127.0.0.1 to see if your network card provides a response. If it responds then the network card hardware is working. If it
is not responding then the network card is either missing, disabled, not configured or broken.
e) Type PING <Your IP Address> where IP address is your netword card's IP address. If that responds then it proves that network data is
being sent out and received by your network card. If it does not respond then either your network card is not configured correctly or broken.
f) Type PING <Router IP Address> where IP address is your router/modem's IP address. If that responds it means your computer can
communicate with another device and that your router or modem is working. If it does not respond then the Router is not configured, is switched off
or broken.
g) Type PING <DNS IP Address> where the IP addess is your DNS server or an ISP's DNS server. IF that responds that means the DNS
server is up and working. If it does not respond then your DNS server is switched off or not configured correctly.
h) Type PING <A web site> where a web site is a known web server such as www.google.com. If that responds that means that the web server
is working AND that DNS name resolution is working. If it says it cannot find the host, then it means it does not exist, is shutdown or DNS address
in your network configuration is incorrect.

3. Testing DNS and name resolution.

To ensure that your computer can connect to the internet it must be able to resolve names so that it can contact web sites, ftp sites, mail servers and so on
using names that you have configured in your software.
a) Type NSLOOKUP in your command prompt.
b) It should display the IP address of your DNS server (which can be your router or your ISP's DNS server). E.g.
Default server: Unknown
Address: 10.0.0.2
>

b) Try typing the name of a PC or server in your local network if you have other computers on your network.
c) Try typing the name of your ISP's web site at the prompt. E.g.
> www.plus.net
Non-authorative answer:
Name: portal.plus.net
Address: 212.159.
8.137
Aliases: www.plus.net

d) If you get 'Unknown, cannot find <name>' then either that web site or server does not exist or dns is not working. Check that the DNS
is configured correctly either on your PC or your modem or router. Ideally, it should be set to something like 'Use Auto Discovered DNS
Servers Only' so that your modem will pick them up automatically. ISPs can change the IP address of their DNS servers some times.
e) Type quit when done.

4. Getting statistics

Once connected, you can gather statistics about your network connection.
a) Netstat -e. Displays network statistics such as bytes sent/received, errors, unknown protocols etc.