User's Manual

Table Of Contents
iRouter Mode
AT+i Programmer‘s Manual Version 8.32 19-2
19 iRouter Mode
19.1 Introduction
iChip‘s iRouter mode is used to provide a gateway to a multitude of LAN or WiFi
devices through a single dialup or cellular link. In this configuration, iChip‘s DHCP
server may be used to assign IP addresses to the local hosts on the LAN/WiFi side. iChip
also uses a Network Address Translator (NAT) to translate between local and public IP
addresses.
While routing IP packets, iChip 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
iChip 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, iChip disconnects its
modem/cellular side and goes offline. After going offline and if ARS=1, iChip will go
online and continue routing when the next packet that requires routing arrives.
Start Router (STRR) command Causes iChip to enter iRouter mode, go online on
the dialup/cellular side, and start routing packets.
Stop Router (STPR) command Causes iChip to exit iRouter mode, go offline on
the dialup/cellular side, and stop routing packets.
19.2 Establishing iRouter mode
iChip 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, iChip immediately goes online on the dialup/cellular side.
Packets are not buffered during dialup/cellular connection establishment. After
establishing the connection, iChip starts the routing service.
19.3 Basic Routing
When iChip 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 LAN/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.