Data Communication and Host Modes
RLXIC-SG
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Intelligent Cellular
User Manual
RadioLinx Intelligent Cellular Serial Modem for Global GPRS/GSM
ProSoft Technology, Inc.
Page 61 of 136
May 29, 2009
*HOSTPRIVMODE
- Set to 1 to enable the explicit IP addresses.
*HOSTPRIVIP
- Set to the IP address you want the RLXIC-SG to give to your
device.
DHCP network Mask
- The subnet mask that is passed to the DHCP client
on the Host device.
*HOSTPEERIP
- Set to the IP address you want for the RLXIC-SG.
*HOSTNETMASK
- Set to the subnetmask, generally 255.255.255.0.
Tip:
If you are using Private Mode (*HOSTPRIVMODE=1), you will need to make sure that
*HOSTPRIVIP and *HOSTPEERIP are on the same subnet. If the subnet mask is 255.255.255.0, it
is safe to use 192.168.x.y for each as long as the x is the same number (0 in the example screen
shot above), and the y is different (1 and 2 in the example), and between 0 and 254.
Note:
Regardless if the RLXIC-SG is configured for Public Mode or Private Mode, the same IP
address will be given to all devices connected to any of the ports. While you can connect with each
to the cellular network and the Internet, you cannot use the RLXIC-SG as a hub or router to
communicate between them.
Internal DHCP Server
DHCP (Dynamic Host Configuration Protocol) has become a primary component
of today's network environments. DHCP allows one server to automatically and
dynamically allocate network IP addresses, and other network related settings
(such as subnet masks, routers, etc.) to each computer or device without the
need to set up each specifically or keep track of what addresses have already
been used.
In a default configuration, the RLXIC-SG acts as a DHCP host to any device
connected to its ports, providing that device with an IP address which can be
used to communicate on the Internet. In Public Mode, that will be the IP address
assigned by the cellular network. In Private Mode, that will be the IP address
defined in *HOSTPRIVIP.
1
When the RLXIC-SG registers on the cellular network, it is assigned an IP
address from your cellular provider, for example, 10.1.2.0.
2
Acting as a DHCP server, in Public Mode, when the RLXIC-SG receives a
DHCP request from an Ethernet device connected via USB, it hands off the
assigned address to the device, and sets up the default gateway address as
10.1.2.1. If the fourth octet is already a 1, it assigns 10.1.2.2 as the router
address.
3
The RLXIC-SG also sends a /24 netmask (255.255.255.0 by default), and
sets up a static route which maps 192.168.13.31 (or the address configured
with *HOSTPEERIP if it is changed) to 10.1.2.1 (or 10.1.2.2 if that was what
the gateway address was given as).
Tip:
When PPPoE is used with the RLXIC-SG, DHCP is not needed. A tunnel is set up connecting
a device (such as your computer or a router) with the modem. The device will then simply use the
MAC address of the RLXIC-SG to send all outgoing packets.
Summary of Contents for RLXIC-SG
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