De RV042
manual:
Enabling multiple subnets (IPv4 only)
Typically, a Cisco RV0xx Series router is used as an access router, with a single LAN subnet. By default, the firewall is pre-configured to deny LAN access if the source IP address is on a different subnet than the router’s LAN IP address. However, you can enable multiple subnets to allow this router to work as an edge device that provides Internet connectivity to different subnets in your LAN.
Step 1 > On the IPv4 tab, check the Enable Multiple Subnet box to enable this feature. Uncheck the box to disable this feature.
Step 2 > Click Add/Edit to create or modify the subnets. After you click the button, the Multiple Subnet Management window appears.
Step 3 > In the pop-up window, add or edit entries as needed.
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Step 4 > When you finish entering settings in the Multiple Subnet window, click OK to save your changes, or click Cancel to undo them.