As a result, the ZyXEL Device resets the connection, as the connection has not been acknowledged.
Figure 84 “Triangle Route” Problem
9.5.2 Solving the “Triangle Route” ProblemYou can have the ZyXEL Device allow triangle route sessions. However this can allow traffic from the WAN to go directly to a LAN computer without passing through the ZyXEL Device and its firewall protection.
Another way to solve the triangle route problem is to use IP alias. IP alias allows you to partition your network into logical sections over the same Ethernet interface. Your ZyXEL Device supports up to three logical LAN interfaces with the ZyXEL Device being the gateway for each logical network. By putting your LAN and Gateway A in different subnets, all returning network traffic must pass through the ZyXEL Device to your LAN. The following steps describe such a scenario.
1A computer on the LAN initiates a connection by sending a SYN packet to a receiving server on the WAN.
2The ZyXEL Device reroutes the packet to Gateway A, which is in Subnet 2.
3The reply from the WAN goes to the ZyXEL Device.
4The ZyXEL Device then sends it to the computer on the LAN in Subnet 1.
Figure 85 IP Alias
Chapter 9 Firewall Configuration | 161 |