Regarding Security patch for your D-Link Devices Firmware updates address the security vulnerabilities in affected D-Link devices. DSL-2750U Wireless N 300 ADSL2+ Modem Router | D-Link
Assign a static IP address to your computer's network card (e.g., IP: 192.168.1.10 , Subnet: 255.255.255.0 ). firmware d-link dsl-2750u h w c1
has 4MB of Flash and 32MB of RAM, which is insufficient for a modern, secure OpenWrt version. Furthermore, OpenWrt support for this device has ended, with 19.07.10 being the final build. Therefore, it is highly recommended to stick with the official D-Link firmware. Regarding Security patch for your D-Link Devices Firmware
Assign a static IP address (like 192.168.1.5 ) to your computer's Ethernet adapter, then try connecting to the gateway again. If you need help finishing the setup, tell me: Furthermore, OpenWrt support for this device has ended,
on your PC to 192.168.1.100 with netmask 255.255.255.0 .