Moxa Technologies MOXA AirWorks User Manual

Page of 52
MOXA AirWorks AWK-1100 User’s Manual 
Troubleshooting 
 
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
 
 
 
 
Communication stages for a client to reach its correspondent host 
For a wireless client computer to communicate with a host on the Internet by the host’s domain 
name (e.g., 
), it first sends a DNS request to a DNS server on the Internet. 
The DNS request travels first to the AP, and 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 correspondent host and sends additional packets to this IP address. 
As illustrated in the above figure, the communication path could be broken at some of the stages. 
The OS-provided network diagnostic tool, ping.exe, can be employed to determine 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. 
y
  Are two or more NICs installed on the client computer? 
¾
  Use the OS-provided command-line network tool, route.exe, to modify the contents of 
the routing table. 
¾
  Use Windows-provided Device Manager to disable unnecessary NICs. 
y
  Is the underlying link (Ethernet or IEEE 802.11g) established? 
¾
  Make sure the Ethernet link is OK. 
¾
  Make sure the wireless settings of the wireless client computer and of the AP match.