Airlink EDGE/GPRS - Manual (Page 36)

PinPoint-E EDGE/GPRS - User Guide, version 2.32 30
Data Communication and Host Modes
Routing, at its most basic level, is the process of forwarding data on to the correct destination.
One component of routing is address determination, directing data to the correct address either as
its final destination or so it can be forwarded on. Selecting gateways where the data can be
directed is another important component of routing.
The PinPoint-E acts as a one to one gateway forwarding messages to and from one device that is
connected to it. The PinPoint-E does not provide routing for any more than that one device.
DHCP in the PinPoint-E using Public Mode
1. When the PinPoint-E registers on the cellular network, it is assigned an IP address from Your
Wireless Service Provider, let’s say A.B.C.D.
2. Acting as a DHCP server, in Public Mode, when the PinPoint-E receives a DHCP request from
an Ethernet device, it hands off the assigned address to the device and sets up the default gate-
way address as A.B.C.1. If the fourth octet is already a 1, it assigns A.B.C.2 as the router
address.
3. The PinPoint-E also sends a /24 netmask (255.255.255.0) and sets up a static route which
maps 192.168.13.31 (or the address configured with *HOSTPEERIP if it is changed) to
A.B.C.1 (or A.B.C.2 if that was what the gateway address was given as).
Private Mode allows more direct control of the gateway address, device address, and netmask that
is given out by the modem’s DHCP server. The IP Address that would be assigned to the end
device is configured in the Private Mode settings (see above). Some applications which rely on
specific IP addressing for their operation may have issues working in Private Mode when the
modem has a non-static IP address.
PPPoE with DHCP
When PPPoE is used with the PinPoint-E, 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
PinPoint-E’s MAC address to send all outgoing packets. To configure your PinPoint-E and your
computer to work with PPPoE, refer to the appendix for PPPoE, page 117.
The AirLink Modem as a Gateway
The primary purpose of the is to forward data from a single device connected to the Ethernet port
to the network and, ultimately, under most circumstances, to the Internet in a one to one gateway
configuration.
When the PinPoint-E obtains its IP Address from the cellular provider, it also obtains Your Wire-
less Service Provider’s routing information necessary to forward messages to Your Wireless Ser-
vice Provider’s routers which can then forward on from there. The PinPoint-E then acts as a router
for the device connected to it, forwarding to or from Your Wireless Service Provider’s network.
Caution: The forwards messages to and from the cellular network for only ONE
device. The is a one-to-one gateway and does not have advanced routing features
required to do one-to-many routing.