Figure 137 Virtual Mapping Of Local And Remote Network Ip Addresses - ZyXEL Communications ZYWALL P1 User Manual

Chapter 13 IPSec VPN
13.6.2.1 Avoiding Overlapping Local And Remote Network IP Addresses
If both IPSec routers support virtual address mapping, you can access devices on both
networks, even if their IP addresses overlap. You map the ZyWALL's local network addresses
to virtual IP addresses and map the remote IPSec router's local IP addresses to other (non-
overlapping) virtual IP addresses.
Take Section 13.6.1.1 on page 219
addresses. You can set up virtual address mapping on both IPSec routers to allow computers
on network X to access network X and network Y computers with the same IP address.
• You set ZyWALL A to change the source IP addresses of packets from local network X
(192.168.1.2 to 192.168.1.4) to virtual IP addresses 10.0.0.2 to 10.0.0.4 before sending
them through the VPN tunnel.
• You set ZyWALL B to change the source IP addresses of packets from the remote
network Y (192.168.1.2 to 192.168.1.27) to virtual IP addresses 172.21.2.2 to 172.21.2.27
before sending them through the VPN tunnel.
• On ZyWALL A, you specify 172.21.2.2 to 172.21.2.27 as the remote network. On
ZyWALL B, you specify 10.0.0.2 to 10.0.0.4 as the remote network.

Figure 137 Virtual Mapping of Local and Remote Network IP Addresses

Computers on network X use IP addresses 192.168.1.2 to 192.168.1.4 to access local network
devices and IP addresses 172.21.2.2 to 172.21.2.27 to access the remote network devices.
Computers on network Y use IP addresses 192.168.1.2 to 192.168.1.27 to access local
network devices and IP addresses 10.0.0.2 to 10.0.0.4 to access the remote network devices.
13.6.2.2 Network Conflict Avoidance (Zero Configuration Mode)
Since your ZyWALL is portable, it may get (or you may need to configure) different WAN
interface settings in different locations. In zero configuration mode, the ZyWALL
automatically overwrites IPSec virtual address mapping settings and IPSec port forwarding
rules (see
220
Section 13.8 on page 228) in order to avoid network conflicts.
as an example of overlapping local and remote IP
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