Usually Zyxel Routers are used in Standard Mode,
which means that the Router handles everything for you such as PPPoE, NAT and Routing.
But besides this Standard Configuration, many Zyxel Routers can be setup in Bridge Mode
and Transparent Mode. In this article, I will explain all three modes, the Transparent
Mode is explained in detail, because there is no simple mouse click within the Router
switch to this very useful mode.
In the example below the following parameters and
terms are used:
PPPoE - Point-to-Point Protocol over
Ethernet, is a network protocol for encapsulating Point-to-Point Protocol (PPP)
frames inside Ethernet frames. You have to enter a User/Password, which you receive
from the Internet Service Provider.
NAT - network address translation is a
technique to receive network
traffic through a router that involves re-writing the source and/or destination IP
addresses and usually also the TCP/UDP port numbers of IP packets as they pass
through. Checksums (both IP and TCP/UDP) must also be rewritten to take account of
the changes. Most systems using NAT do so in order to enable multiple hosts on a
private network to access the Internet using a single public IP address.
HSZ - This is the Private Network (LAN),
usually in the IP Range 192.168.XXX.XXX
(in the Example 192.168.1.0 /
255.255.255.0 is used).
DMZ - This is the Public Network, which
can be seen from the Internet
(in the Example 188.8.131.52 / 255.255.255.240 is used).
In the Standard Mode, no extra Router / Firewall is
used. The HSZ is directly connected the Zyxel Router which gets its Public Address
184.108.40.206 from the Provider. The HSZ IP-Address for
the Zyxel Router is 192.168.1.1, all
hosts in the HSZ are using this IP-Address as the Default Gateway. The Zyxel Router
handles all relevant functions PPPoE, Routing and NAT Translation. The Zyxel configuration
is very simple and need no special setup, I do not explain this mode in more
In Bridge mode, you must either have another device
(a Router/Firewall or your PC) to use that can be configured for PPPoE authentication.
The Public IP-Address (220.127.116.11) is forwarded to the Router/Firewall. In Bridge Mode, the Zyxel
Router, delegates the main functions PPPoE, Routing and NAT to the connected Router/Firewall. This configuration is useful if you have a DMZ and a Router/Firewall which
can handle the PPPoE authentication. The Zyxel configuration is again very simple, just
click the Bridge Switch, but now you have to configure the Router/Firewall.
In Transparent mode (which usually is NOT documented
in the Zyxel doc) you have the same advantages as in the bridge mode, but you do not need
a Router/Firewall that is able to do the PPPoE authentication, the Zyxel Router can do
it as in the Standard Mode. The Public IP-Address (18.104.22.168) is now on the
site of the Zyxel Router. We use a Cisco 2600 Router/Firewall, which is very
complicated to setup for the PPPoE authentication - with the Zyxel Router in Transparent
mode we can further use the Cisco 2600 Router.
Setup the PPPoE authentication (User, Password,
IP automatic from ISP)
Menu NAT -> Switch off NAT -> Apply
Menu LAN -> DHCP to «None» ->
Router IP Address to 22.214.171.124 (same IP as
received on WAN)
Subnet to 255.255.255.240 -> Apply
Setup IP-Address on Public Interface to
Setup Default Gateway to
Standard and Bridge Modes are
well documented - in fact often the Bridge Mode is called
Transparent Mode. In this example we present the real Transparent
Mode which has the same advantages as the Bridge Mode, but with
the difference, that nothing must be changed on an existing Router/Firewall.