Local DHCP with WDS

I have OpenWRT installed on a Deco M4R, with WDS configured and working. This is a lab environment, and one of the things I'd like to do is to enable PXE booting via TFTP for thin clients I have set up in the lab. For some reason, on the main network, I can see the WDS client in the lab, but cannot see any of the devices I have connected to that WDS, via ethernet or wireless. They do get IPs assigned, and can reach the internet, as well as other devices that are connected directly to the main network, so it seems that DHCP is working from the main network.

The connection, however, is sometimes unstable. Also, for some reason, even with the correct DHCP options (66 & 67) configured correctly, the thin clients I want to boot via PXE cannot get a response from the DHCP server. I also cannot get a response using nmap when connected to the WDS client.

What I'd like to do is to configure DHCP locally on the lan interface of the WDS client, and have it hand out IP addresses. That does work, even with WDS, and I can boot my thin clients from the TFTP server locally, but they cannot reach the internet. I don't necessarily care about reaching other devices upstream, but the internet is a must. Is this something that can be done?

I do like WDS because it really simplifies the configuration, and even though it's sometimes unstable, I do find that it's more reliable than configuring a wifi repeater/extender. If I could keep the WDS configuration that would be ideal.

The configuration you describe is called wwan, no need for WDS at all.

WDS should work as a true layer 2 bridge like an Ethernet cable, and you should not be having these problems.

One thing to check is make sure the DHCP servers are disabled in all devices except the main router. Running more than one DHCP server on the same L2 network is a very advanced topic and OpenWrt is not set up for it.

1 Like

@mk24 thanks.

After some further research and experimentation, what I found was that if I set up dnsmasq as a DHCP relay, it will successfully relay DHCP requests from the WDS client to the DHCP server. I'm not exactly sure why I needed to do this, but it did solve the issue I was facing.

It is worth noting the upstream AP is a TP-Link Omada system, which I believe may actually run OpenWRT under the hood, but is configured through the Omada controller software. I didn't need to make any configuration changes in the Omada controller, just in the WDS client router.

2 Likes

They certainly do not run openwrt compatible mesh and wds . Quite fresh idea to use dhcp relay in place of nat

Thanks. There arent any options to enable or configure WDS on the controller software afaict. I was surprised that everything "just worked" when I set up WDS on the OpenWRT router. I wasnt able to reach the devices connected to OpenWRT router from the main network, although I could reach everything from TP Link side on my OpenWRT router. I wasn't concerned with it initially, but it became obvious something was wrong when I started trying to configure PXE boot options on the TP Link system. Pretty quickly saw it was related to DHCP and just by chance stumbled over the DHCP relay option for dnsmasq, and luckily it worked.

I'm able to reach all the devices in the network now as well, from both sides. :slight_smile:

There have been surprise cases different vendors WDS was compatible, but it is non-standard, how one device interprets extra MAC address pair in wifi packet....

1 Like