Security Considerations; Triangle Route - ZyXEL Communications P-2612HW-F1 User Manual

12.5.3 Security Considerations

Note: Incorrectly configuring the firewall may block valid access or introduce security
risks to the ZyXEL Device and your protected network. Use caution when
creating or deleting firewall rules and test your rules after you configure them.
Consider these security ramifications before creating a rule:
Does this rule stop LAN users from accessing critical resources on the Internet?
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For example, if IRC is blocked, are there users that require this service?
Is it possible to modify the rule to be more specific? For example, if IRC is blocked
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for all users, will a rule that blocks just certain users be more effective?
Does a rule that allows Internet users access to resources on the LAN create a
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security vulnerability? For example, if FTP ports (TCP 20, 21) are allowed from the
Internet to the LAN, Internet users may be able to connect to computers with
running FTP servers.
Does this rule conflict with any existing rules?
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Once these questions have been answered, adding rules is simply a matter of
entering the information into the correct fields in the web configurator screens.

12.5.4 Triangle Route

When the firewall is on, your ZyXEL Device acts as a secure gateway between
your LAN and the Internet. In an ideal network topology, all incoming and
outgoing network traffic passes through the ZyXEL Device to protect your LAN
against attacks.
Figure 135 Ideal Firewall Setup
12.5.4.1 The "Triangle Route" Problem
A traffic route is a path for sending or receiving data packets between two
Ethernet devices. You may have more than one connection to the Internet
(through one or more ISPs). If an alternate gateway is on the LAN (and its IP
address is in the same subnet as the ZyXEL Device's LAN IP address), the
P-2612HW-F1 User's Guide
LAN
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Chapter 12 Firewall
WAN
Internet
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