Datasheet

APPLICATION NOTE - Configuring the CX111 for the SSG Series

Description and Deployment Scenario

The CX111 ships with a default configuration that should accommodate most deployment scenarios. The deployment

model assumes that the CX111 is connected to a DHCP-enabled interface.

Figure 1: Deployment model

The CX111 will maintain the wireless modem (or modems, if more than one modem is used) in a disconnected

state, and will trigger a new connection as soon as the SSG Series device requests a new lease and initiates data

transfer. Modem(s) will be disconnected only when no interesting traffic passes through for an idle amount, and only

reconnected when interesting traffic starts again. The idle timeout default is 20mins and can be changed by using the

CX111’s Web UI.

When using the 3G link as the primary connection, long lease times can be used, as generally there won’t be a need to

constantly connect and disconnect the line. On the other hand, if the bridge is used to provide a backup connection,

short lease times (in the order of a minute) are commonly used, so when the primary link is active, the backup link can

be disabled, triggering a disconnection, in the worse case, after a lease time.

The CX111 assigns the address received from the wireless service provider to the gateway (normally this is a public

address). For obvious reasons, only a single device can be connected to the CX111 at any given time, or else multiple

devices will contend for the only address passed to the CX111. The CX111 works in “pass through” mode, simply relaying

all traffic from the wireless network to the DHCP client.

Management Interface

The CX111 provides a Web-based management interface, and it can be accessed even when 3G modems are not used.

Since “pass through” mode is used (instead of a routed connection, with the bridge doing Network Address Translation

(NAT)), the management interface cannot be accessed through the normal data channel. When the modem is not

active or not inserted, a 192.168.30.x/24 network address is provided to the SSG Series platform and 192.168.30.1

becomes the temporary management address for the CX111.

The management interface is still accessible through the Ethernet port, but VLAN tagging is used to separate

management form data traffic using the following parameters

Table 1: Management Network Settings

CARD MODEL WIRELESS TECHNOLOGY

Management subnet 192.168.0.0/24

Management address 192.168.0.1

VLAN ID 3900

192.168.1.0/24

Trust Zone

CX111

SSG Series

OFFICE

INTERNET

Deployment

The CX111 acts as a DHCP server and relays the public

address obtained from the 3G network to the SSG Series.