Appendix J Triangle Route; Figure 222 Ideal Setup; The Ideal Setup - ZyXEL Communications 802.11g HomePlug AV ADSL2+ Gateway P-660HWP-Dx User Manual

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P P E N D I X

The Ideal Setup

When the firewall is on, your P-660HWP-Dx 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 P-660HWP-Dx to protect your LAN against attacks.

Figure 222 Ideal Setup

The "Triangle Route" Problem
A traffic route is a path for sending or receiving data packets between two Ethernet devices.
Some companies have more than one route to one or more ISPs. If the alternate gateway is on
the LAN (and it's IP address is in the same subnet), the "triangle route" problem may occur.
The steps below describe the "triangle route" problem.
1 A computer on the LAN initiates a connection by sending out a SYN packet to a
receiving server on the WAN.
2 The P-660HWP-Dx reroutes the SYN packet through Gateway A on the LAN to the
WAN.
3 The reply from the WAN goes directly to the computer on the LAN without going
through the P-660HWP-Dx.
As a result, the P-660HWP-Dx resets the connection, as the connection has not been
acknowledged.
P-660HWP-Dx User's Guide
Triangle Route
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