Table 67 Security > Firewall > Default Rule (Bridge Mode) - ZyXEL Communications ZyWall 5 Series User Manual

The following table describes the labels in this screen.
Table 67 SECURITY > FIREWALL > Default Rule (Bridge Mode)
LABEL
Enable Firewall
Allow
Asymmetrical
Route
From, To
Log
Chapter 11 Firewall
DESCRIPTION
Select this check box to activate the firewall. The ZyWALL performs access control
and protects against Denial of Service (DoS) attacks when the firewall is activated.
If an alternate gateway on the LAN has an IP address in the same subnet as the
ZyWALL's LAN IP address, return traffic may not go through the ZyWALL. This is
called an asymmetrical or "triangle" route. This causes the ZyWALL to reset the
connection, as the connection has not been acknowledged.
Select this check box to have the ZyWALL permit the use of asymmetrical route
topology on the network (not reset the connection).
Note: Allowing asymmetrical routes may let traffic from the WAN go
directly to the LAN without passing through the ZyWALL. A
better solution is to use IP alias to put the ZyWALL and the
backup gateway on separate subnets. See
page 229 for an example.
Set the firewall's default actions based on the direction of travel of packets. Here are
some example descriptions of the directions of travel.
From LAN To LAN means packets traveling from a computer on one LAN subnet to
a computer on another LAN subnet on the LAN interface of the ZyWALL or the
ZyWALL itself. The ZyWALL does not apply the firewall to packets traveling from a
LAN computer to another LAN computer on the same subnet.
From VPN means traffic that came into the ZyWALL through a VPN tunnel and is
going to the selected "to" interface. For example, From VPN To LAN specifies the
VPN traffic that is going to the LAN. The ZyWALL applies the firewall to the traffic
after decrypting it.
To VPN is traffic that comes in through the selected "from" interface and goes out
through any VPN tunnel. For example, From LAN To VPN specifies the traffic that is
coming from the LAN and going out through a VPN tunnel. The ZyWALL applies the
firewall to the traffic before encrypting it.
From VPN To VPN means traffic that comes in through a VPN tunnel and goes out
through (another) VPN tunnel or terminates at the ZyWALL. This is the case when
the ZyWALL is the hub in a hub-and-spoke VPN. This is also the case if you allow
someone to use a service (like Telnet or HTTP) through a VPN tunnel to manage the
ZyWALL. The ZyWALL applies the firewall to the traffic after decrypting it.
Note: The VPN connection directions apply to the traffic going to or
from the ZyWALL's VPN tunnels. They do not apply to other
VPN traffic for which the ZyWALL is not one of the gateways
(VPN pass-through traffic).
Here are the default actions from which you can select.
Select Drop to silently discard the packets without sending a TCP reset packet or an
ICMP destination-unreachable message to the sender.
Select Reject to deny the packets and send a TCP reset packet (for a TCP packet)
or an ICMP destination-unreachable message (for a UDP packet) to the sender.
Select Permit to allow the passage of the packets.
Select this to create a log when the above action is taken.
ZyWALL 5/35/70 Series User's Guide
Section 11.6.1 on
233