Technical information

Chapter 2: AT+i Commands Reference
May 31, 2008 AT+i Commands Reference Manual 2-51
iRouter Mode
Introduction
W24's iRouter mode is used to provide a gateway to a multitude of WiFi devices through a single
dialup or cellular link. In this configuration, W24's DHCP server may be used to assign IP
addresses to the local hosts on the WiFi side. W24 also uses a Network Address Translator (NAT)
to translate between local and public IP addresses.
While routing IP packets, W24 also accepts AT+i commands, as during normal operation. The
CPF (Communication Platform) parameter selects which interface to use for Internet-related
AT+i commands.
The following parameters and commands are used to configure iRouter mode behavior:
• Automatic Router Start (ARS) parameter - When set to 1, this parameter causes W24 to go
online in iRouter mode upon power-up and start routing packets.
• Inactivity Timeout (IATO) parameter - When in iRouter mode, if no routing activity is
detected for the period of time specified by this parameter, W24 disconnects its
modem/cellular side and goes offline. After going offline and if ARS=1, W24 will go online
and continue routing when the next packet that requires routing arrives.
• Start Router (STRR) command - Causes W24 to enter iRouter mode, go online on the
dialup/cellular side, and start routing packets.
• Stop Router (STPR) command - Causes W24 to exit iRouter mode, go offline on the
dialup/cellular side, and stop routing packets.
Establishing iRouter Mode
W24 can be entered into iRouter mode using one of two possible methods:
• When the ARS parameter is set to 1, automatically and immediately after power-up and after
every soft reset induced by AT+iDOWN.
• By issuing the AT+iSTRR (Start Routing) command.
Upon entering iRouter mode, W24 immediately goes online on the dialup/cellular side. Packets
are not buffered during dialup/cellular connection establishment. After establishing the
connection, W24 starts the routing service.
Basic Routing
When W24 is in iRouter mode, it routes packets between its two communication platforms
utilizing a Network Address Translator (NAT) to translate between the internal IP address space
used on the WiFi side and the real IP address used on the dialup/cellular side.
The NAT translates internal IP addresses of outgoing packets to the real IP address space and
makes the reciprocal translation of packets received in response.
Note: When using an FTP client to connect to an external FTP server through the iRouter, you
must use the FTP client in passive mode. For example, if the FTP client is a W24, you
must open the FTP session using AT+i@FTP.