Chapter 12 NAT
ZyWALL ATP Series User’s Guide
339
Figure 230 LAN to LAN Traffic
The LAN SMTP server replies to the Zyxel Device’s LAN IP address and the Zyxel Device changes the
source address to 1.1.1.1 before sending it to the LAN user. The return traffic’s source matches the
original destination address (1.1.1.1). If the SMTP server replied directly to the LAN user without the traffic
going through NAT, the source would not match the original destination address which would cause the
LAN user’s computer to shut down the session.
Figure 231 LAN to LAN Return Traffic
192.168.1.21
LAN
192.168.1.89
Source 192.168.1.89
SMTP
NAT
Source 192.168.1.1
SMTP
192.168.1.21
LAN
192.168.1.89
Source 1.1.1.1
SMTP
NAT
Source 192.168.1.21
SMTP
To Next Page
Loading...
