OpenWRT on TP-Link WR840N v11 – DHCP Issue

Hi everyone,

I recently installed OpenWRT (openwrt-ar71xx-tiny-tl-wr841-v11-squashfs-factory.bin) on my TP-Link WR840N v11 router. I realize this firmware is meant for the TL-WR841 v11, but it installed successfully. However, I’m experiencing network issues, particularly with DHCP assigning duplicate IPs.

My Current Network Setup:

  1. ISP/Modem (Static IP)Dumb Switch (No VLAN/LAGG support)
  2. The Dumb Switch connects to:
  • Other users in the network
  • OpenWRT router (TP-Link WR840N v11)
  1. OpenWRT Router connects to:
  • OPNsense firewall
  • Windows Server

The Problem:

  • OpenWRT is assigning the same IP (e.g., 192.168.1.225) to multiple devices, causing conflicts.
  • Devices connected to the OpenWRT WiFi or LAN/WAN ports are getting IPs from the same range as the main network, but DHCP is not handling them correctly.
  • I suspect this is due to a misconfiguration in DHCP or an issue with the firmware compatibility.

What I Want to Achieve:

  • The Windows Server should receive a DHCP IP from the main network (192.168.1.x) rather than OpenWRT assigning it separately.
  • OpenWRT should act as a bridge (Dumb AP) or DHCP relay rather than running its own DHCP server.
  • All devices should be on the same subnet without conflicts.

OpenWrt 18.06 is EOL for over half a decade now and no longer supported, it does contain unfixed security issues that aren't going to be fixed. It is insecure to use this version for any purpose, including wireless ones. The ar71xx target has been replaced with the DTS based ath79 target, which is considerably different from the old mach file based SOC support.

Due to its insufficient system specifications, this device hasn't been supported in over half a decade and cannot run modern (supported) versions of OpenWrt, you need to upgrade the hardware before running modern OpenWrt.

The second hand markets tend to have quite decent hardware that does meet OpenWrt's minimum system requirements and will run circles around the tl-wr841nd v11.

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