OpenWrt/LEDE Project

  • Status Unconfirmed
  • Percent Complete
  • Task Type Bug Report
  • Category Kernel
  • Assigned To No-one
  • Operating System All
  • Severity Medium
  • Priority Very Low
  • Reported Version openwrt-19.07
  • Due in Version Undecided
  • Due Date Undecided
  • Private
Attached to Project: OpenWrt/LEDE Project
Opened by Lee Chantrey - 21.05.2020

FS#3113 - Failed to receive offered IP address for devices at random time intervals

Hardware: TP-LINK Archer C9 V1
Version: OpenWrt 19.07.2 r10947-65030d81f3

The Archer C9 is the only device doing any NAT on the network and is the only DHCP service on the network. To get around the fact that BCM4360 has no drivers I installed a WiFi Dongle. The Archer C9 is the gateway to the internet.

Sometimes any device at random when connecting to the gateway will be unable to acquire an IP Address despite the fact that the system log clearly shows it offered an IP address to a device with the same mac address. There’s a definite working physical link between the device and gateway. Connecting to alternative ‘dumb APs’ on the same network as the gateway results in the same problem; Unable to acquire an IP address. Asking the device’s DHCP client to renew the address does not help.

I have always experienced this problem with this router when using any non stock firmware (I.E all builds of DD-WRT that I tried seemed to exhibit the same behavior) otherwise I would have said it was a problem specific to only this hardware. If left long enough (Several hours) eventually the device will receive it’s an IP address again. Stock firmware did not once exhibit this behavior in the 2 years+ I had it running.

Eventually I set the device’s IP address manually to the exact IP Address being offered by the DHCP server. The device was still unable to ping the gateway.
I then tried to set the device’s IP address to a random IP address (within the range of IP addresses the DHCP server could potentially serve) The device was still unable to ping the gateway. Finally I set the device IP address outside of the range being offered by the DHCP server and then it was able to communicate with the gateway.

I have attached the system log of when a device failed to acquire an IP address. I have replaced all mac addresses and IP addresses with randomly generated mac addresses and IP addresses. ‘1b:ac:8b:93:55:ba’ is the device struggling to acquire the IP address. It is a MacBook Pro. If memory serves correctly devices requesting an IP address in the same time period will also fail to acquire a IP address from the DHCP server, further testing is required for me to prove that though. Other services including NAT translation for pre-allocated devices appears to behave as expected. The gateway will function as expected in every other way. The log will show me successfully logging via my Android device during the time it was happening.


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