ZyXEL Communications P-3202HN-Ba User Manual page 156

Chapter 12 Firewalls
As a result, the IAD resets the connection, as the connection has not been
acknowledged.
Figure 72 "Triangle Route" Problem
12.5.3.2 Solving the "Triangle Route" Problem
If you have the IAD allow triangle route sessions, traffic from the WAN can go
directly to a LAN computer without passing through the IAD and its firewall
protection.
Another solution is to use IP alias. IP alias allows you to partition your network
into logical sections over the same Ethernet interface. Your IAD supports up to
three logical LAN interfaces with the IAD being the gateway for each logical
network.
It's like having multiple LAN networks that actually use the same physical cables
and ports. By putting your LAN and Gateway A in different subnets, all returning
network traffic must pass through the IAD to your LAN. The following steps
describe such a scenario.
A computer on the LAN initiates a connection by sending a SYN packet to a
1
receiving server on the WAN.
The IAD reroutes the packet to Gateway A, which is in Subnet 2.
2
The reply from the WAN goes to the IAD.
3
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LAN
1
2
3
WAN
ISP 1
ISP 2
A
IAD User's Guide