Transparent Firewalls; Configuring Device Mode (Router) - ZyXEL Communications ZYWALL 35 User Manual

Chapter 32 Maintenance

32.7 Transparent Firewalls

A transparent firewall (also known as a transparent, in-line, shadow, stealth or bridging
firewall) has the following advantages over "router firewalls":
1 The use of a bridging firewall reduces configuration and deployment time because no
networking configuration changes to your existing network (hosts, neighboring routers
and the firewall itself) are needed. Just put it in-line with the network it is protecting. As
it only moves frames between ports (after inspecting them), it is completely transparent.
2 Performance is improved as there's less processing overhead.
3 As a transparent bridge does not modify the frames it forwards, it is effectively "stealth"
as it is invisible to attackers.
Bridging devices are most useful in complex environments that require a rapid or new firewall
deployment. A transparent, bridging firewall can also be good for companies with several
branch offices since the setups at these offices are often the same and it's likely that one design
can be used for many of the networks. A bridging firewall could be configured at HQ, sent to
the branches and then installed directly without additional configuration.

32.8 Configuring Device Mode (Router)

Click MAINTENANCE > Device Mode to open the following screen. Use this screen to
configure your ZyWALL as a router or a bridge.
In router mode, the ZyWALL functions as a router. The ZyWALL routes traffic traveling
between the ZyWALL's interfaces and filters and inspects packets.
In router mode, the ZyWALL can provide multiple WAN with load balancing (including 3G
on the ZyWALL 5). It can also get an IP address from a DHCP server. It can also serve as a
DHCP server to assign IP addresses to your local computers. The LAN, WAN, DMZ and
WLAN interfaces all have different IP addresses. The ZyWALL also provides NAT, port
forwarding, policy routing, and DNS in router mode. These features allow you to set up
private network. See
mode.
The following screen displays when the ZyWALL is in router mode.
582
Table 6 on page 74 for a detailed list of other features available in router
ZyWALL 5/35/70 Series User's Guide