ZyXEL Communications P-792H User Manual page 137

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 P-792H v2 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 P-792H v2 reroutes the packet to Gateway A, which is in Subnet 2.
2
The reply from the WAN goes to the P-792H v2.
3
The P-792H v2 then sends it to the computer on the LAN in Subnet 1.
4
Figure 59 IP Alias
LAN
P-792H v2 User's Guide
Subnet 1
1
4
2
3
Subnet 2
WAN
ISP 1
ISP 2
A
Chapter 9 Firewalls
137