User guide

ALEOS 4.2.3 User Guide

52 20080616

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 AirLink device acts as a DHCP host to any device

connected to its ports. This DHCP host provides 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 addresses defined in the LAN pages.

Address Assignment in Public Mode

1. When the AirLink device registers on the cellular network, it is assigned an IP

address from the carrier, e.g., 10.1.2.0.

2. When using a specific interface, the AirLink device acts as a DHCP server

unless disabled. When the Host Connection Mode is Ethernet Uses Public IP,

and the AirLink device receives a DHCP request from an Ethernet device

connected to its ports, 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 value is

already a 1, it assigns 10.1.2.2 as the router address.

Note: The primary gateway to the cellular network, for any connected device, is enabled

by default.

3. The AirLink device 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 AirLink device, the DHCP server needs to be disabled.

A tunnel is set up connecting a device (such as your computer or a router) with the AirLink

device. The device will then use the MAC address of the AirLink device to send all

outgoing packets.