DHCP not working on 2.4Ghz wireless

[MartinNL]

TLDR: Got 3 routers. On my main ASUS RT-AC68U router (merlin 380.57), clients connecting to the 2.4Ghz wireless are not receiving a dhcp lease.

I have 3 routers, 1 on each floor:

• 1st floor
  • ASUS RT-AC68U with merlin 380.57
  • Operation mode: wireless router
  • IP: 10.10.10.1
  • 2.4Ghz on channel 6
  • 5Ghz on channel 64
• 2nd floor
  • ASUS RT-AC68U with merlin 380.57
  • Operation mode: Access Point
  • IP: 10.10.10.2
  • 2.4Ghz channel 1
  • 5Ghz channel 108
• 3rd floor
  • Linksys E4200 with default v1.0.01
  • Operation mode: semi-bridge mode
    • No Internet config, No DHCP
  • IP: 10.10.10.3
  • 2.4Ghz channel 12
  • 5Ghz channel 36

All wireless access points have the same name, like "WiFi" for 2.4Ghz and "WiFi5" for 5Ghz. They also share the same password.

On the main router on the 1st floor, DHCP range is setup from 10.10.10.200 to 10.10.10.240. All other addresses within the 10.10.10.x range are for manual reservations.

There are about 40 DHCP reservations in the list.

For the last couple of weeks (I guess since the time I updated to Merlin 380.57) sometimes mobile phones would have a wireless connection, but did not have internet access.
This could be fixed by disabling and re-enabling WiFi on the phone.
Today I was fed up by this, so I tried to figure out what was going on.
I knew that switching WiFi connection would get the internet connectivity back, so my 1st guess was I connected to a "broken" WiFi access point.
I renamed all of the access points, so I could easily identify which AP I was connected to.
Every access point I connected to worked, except for the main routers 2.4Ghz AP. When connecting to that AP, the client (my phone) got an 192.168.192.x address.

My phone is in the DHCP reservation list with IP 10.10.10.150. On all other AP's, including the 5Ghz on the main router, it got that IP address.

To be sure it wasn't a DHCP reservation bug, I removed the reservation. This did not resolve anything.

For now, I have disabled the 2.4Ghz on the main router (well, changed password so it won't match and client won't connect anymore)

Does anybody have a clue how to fix this?
Or could this be a bug in the 380.57 firmware?

 

[sfx2000]

Every access point I connected to worked, except for the main routers 2.4Ghz AP. When connecting to that AP, the client (my phone) got an 192.168.192.x address.

Intentional or not - sounds like there's another DHCP server running somewhere... even if it's one that is not intended...

 

[MartinNL]

Thanks for the find! I only searched for DHCP in post-titles prior to posting, thinking the number of post with the word DHCP in it would overwhelm me.