User's Manual

Chapter 10 Firewalls
P-660HW-Tx v3 Series User’s Guide
209
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 ZyXEL Device to your LAN. The following
steps describe such a scenario.
1 A computer on the LAN initiates a connection by sending a SYN packet to a
receiving server on the WAN.
2 The ZyXEL Device reroutes the packet to Gateway A, which is in Subnet 2.
3 The reply from the WAN goes to the ZyXEL Device.
4 The ZyXEL Device then sends it to the computer on the LAN in Subnet 1.
Figure 86 IP Alias
1
2
3
LAN
A
ISP 1
ISP 2
4
WAN
Subnet 1
Subnet 2