ZyXEL ADSL Prestige 2602R-61 VoIP 91-006-024004B Manual Do Utilizador

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Prestige 2602R Series User’s Guide
Appendix E Triangle Route
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Triangle Route
The Ideal Setup 
When the firewall is on, your Prestige 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 Prestige to protect your LAN against attacks.
Figure 254   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 alternate route to one or more ISPs. If the LAN and 
ISP(s) are in the same subnet, the “triangle route” problem may occur. The steps below 
describe the “triangle route” problem. 
A computer on the LAN initiates a connection by sending out a SYN packet to a 
receiving server on the WAN.
The Prestige reroutes the SYN packet through Gateway on the LAN to the WAN. 
The reply from the WAN goes directly to the computer on the LAN without going 
through the Prestige. 
As a result, the Prestige resets the connection, as the connection has not been acknowledged.