SMC Networks BR21VPN - annexe 1 Manual page 52

DMZ:
The Administrator uses the DMZ Interface to set up the DMZ network.
The DMZ includes:
NAT Mode：In this mode, the DMZ is an independent virtual subnet.
This virtual subnet can be set by the Administrator but cannot be the
same as LAN Interface.
Transparent Mode: In this mode, the DMZ and WAN Interface are in
the same subnet.
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