Windows DHCPv4 not working

Stock flash from latest release (not snapshot) and it seems DHCP doesn't work. Can anyone confirm, stock configs.

Same device, same LEDE version, DHCP works for me...

Which is really strange, logread shows DHCPDISCOVERY and DHCPOFFER but nothing gets assigned, I've tried multiple devices from windows, android to apple and all have the same issue.

On the Windows devices, open a command prompt and run...

ipconfig /release

ipconfig /renew

It's an autoconfigured ipv4, you cannot release a autoconf ipv4

What happens if you reboot the WRT3200ACM?

  1. I enabled DHCP logging on a windows client
  2. Saw Offer Receive Timeout has happened on the interface X
  3. Apparently Windows 7 and up (and other devices ?!?) block DHCP relay traffic on public networks.
  4. The fix is to either change to private network or allow unicast response to multicast or broadcast requests.

@nvm DHCP relay and unicast traffic should always be blocked on a public network for security reasons.

Out of curiosity, why is your network listed as a public network? The only way Windows will auto identify a network as public is if it has a non RFC1918 IP, or if the network adapter is virtual adapter (Hyper-V Private adapter for example).

  • If using Win 7, you can assign a network as Private or Public via the Control Panel.
    • In Windows 8+, this is no longer possible. To force a network as Private, if it's identified as Public, either:
      • Requires Win 8/10 Pro, as it requires group policy [gpedit.msc], via secpol.msc
      • Requires a registry edit, changing a hex value for that network under Network List

If the network needs to remain public, create firewall rules on the client as follows, then once the client has received an IP from the DHCP Server, disable 1 & 2:

  1. Allow Inbound UDP from Any on 67-68 to Any on UDP 67-68
  2. Allow Outbound UDP to Any on 67-68 from Any on UDP 67-68
  3. Allow Outbound TCP/UDP to Any on 53