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B-2: TCP/IP Settings Problems
Default Gateway
of Client Computer
AP
IEEE 802.11g
Stage A State B
Correspondent
Host
Stage D
Client
Computer DNS Server
of Client Computer
Ethernet LAN
Internet
Fig. 60. Communication stages for a client to reach its correspondent host.
For a wireless client computer to communicate with a correspondent host on the Inter-
net by the host’s domain name (e.g. http://www.wi-fi.com), it first sends a DNS request
to a DNS server on the Internet. The DNS request travels first to the AP, then the AP
relays this request to the default gateway of the client computer. Finally, this request is
forwarded by the gateway to the DNS server on the Internet. The DNS reply issued by
the DNS server is transmitted back to the client computer following a reverse path.
When the client computer receives the DNS reply, it knows the IP address of the corre-
spondent host and sends further packets to this IP address.
As illustrated in Fig. 60, the communication path could be broken at some of the stages.
The OS-provided network diagnostic tool, ping.exe, can be employed to find out
TCP/IP-related communication problems.
NOTE: If two or more NICs are installed and operating on a client computer, TCP/IP
may not work properly due to incorrect entries in the routing table. Use the OS-provided
command-line network tool, route.exe, to add or delete entries from the routing table.
Or, use Windows-provided Device Manager to disable unnecessary NICs.
Solve the following problems in order:
• The AP does not respond to ping from the client computer.
Are two or more NICs installed on the client computer?