I recently added a D-Link Wi-Fi extender, tested it in both wired AP mode and wireless extender mode, both working fine. But one point still puzzles me, maybe somebody here knows?

Right now my main router is is issuing the DHCP addresses for clients on the extender WiFi in either mode, which is normal and what I want, to have everything on the same LAN.

Under what circumstance would the extender create its own LAN and act as a DHCP server issuing the IP addresses in its own range separate from my main router? Many sources say this is a common alternative option with extenders, but the D-Link user manual is silent on this issue. There does not appear to be any setting on the D-Link extender addressing this. The only setting related to DHCP is to enable/disable it for getting a client IP address from the main router when connecting wirelessly. Wouldn’t there have to be a setting for the DHCP address range if the extender supports acting as a DHCP server? Is that functionality not supported at all on this model DAP-1755 (AC1750)?