DHCP only working on AIMesh node 2.4gHz - why?

[Mastiff]

This is something of the weirdest I've seen in my 20 years of having a Windows Server at home, and my 35 years of computing! When I connect anything to the main access point in my AIMesh, which is two RT-AC88U with the latest Merlin, I can't get DHCP, and requests time out on ipconfig /renew. If I do that while connected to the node's 5 gHz network, I see the same. But if I connect to the node's 2.4 gHz network, it works!

I have set up a new server this week, going from Windows Server 2016 to 2019, and if I reboot into the old setup, everything works. On wired network it works all the time. So something's different in the setup, but I can't imagine what, and why the mesh is the only thing that notices it. I have of course done more reboots and restarts than I care to think of this weekend, and I have gone thorugh the DHCP setup of the server several times, without finding anything. Does anybody have a suggestion to what I should try? I will probably try to reset the server's DHCP service and set it up all again, but I doubt that will do anything since it works on the wired network.

 

[Mastiff]

The solution was no less weird! I saw a kink in the network cable that went from the server to the main AIMesh AP and tested with another cable, just to make sure. And suddenly everything works! I can understand most of the stuff not working because of a bad cable, but only the one band no the AIMesh NODE working, and no bands on the AIMesh AP is totally beyound my imagination. It's not"remembered" either, because I did several DNS cache flushes and resets of the wireless network, so it can't possibly have remembered anything. Well, at least it's working...and I get to be annoyed because a bad cable cost me hours of work!

 

[L&LD]

Yes, when things don't make sense, start at the beginning and work slowly/methodically while testing at each step in the process.

Glad you found the solution at last.

 

[OzarkEdge]

The solution was no less weird! I saw a kink in the network cable that went from the server to the main AIMesh AP and tested with another cable, just to make sure. And suddenly everything works! I can understand most of the stuff not working because of a bad cable, but only the one band no the AIMesh NODE working, and no bands on the AIMesh AP is totally beyound my imagination. It's not"remembered" either, because I did several DNS cache flushes and resets of the wireless network, so it can't possibly have remembered anything. Well, at least it's working...and I get to be annoyed because a bad cable cost me hours of work!

Good catch! Someone told me once that 99% of all networking problems are cabling... we were using arcnet/coax. Probably not fully true but it stuck with me and keeps me checking interconnects first when troubleshooting oddness.

OE

 

[Mastiff]

Well, that error wasn't everything. Even with a new cable DHCP doesen't work on the main AP's 2.4gHz! It works on both the node's channels and the AP's 5gHz, but not on the 2.4. And I'm out of ideas...

 

[Mastiff]

And finally I found the real answer! Setting the bandwith to 20 MHz only fixed it. I found it in this ancient thread:
https://www.snbforums.com/threads/no-dhcp-handout-on-2-4ghz.8783/

So at last my system works for all devices!