RAX120 DHCP Issues

I first want to say I been using Netgear products since the 54g days so I am familiar with them. However ever since I got FIOS back on 08 I haven’t used my Netgear routers as DHCP servers. 

My last router was the R8500 which worked fine until I decided to remove the FIOS Gateway router and just use the R8500 as the DHCP server. That is when I started noticing a weird issue where randomly the router will kill all WiFi connections. The devices would re-connect usually after a few seconds but some didn’t. I couldn’t find a solution to that so I upgraded to the RAX120 hoping its price tag would make up for the vast number of devices I have.

So the RAX120 works great when it works without the weird all device disconnect of the R8500. The only problem was that randomly once or twice a day devices would drop their connection. Sometimes they would lose Wi-Fi, I saw once a self-assigned ip get set, and other times it would be connected with a valid IP but no internet access.

After a few weeks of digging, firmware upgrades/downgrades I think I figured out the issue. I have 20 or so devices that are always connected (3 wired, 4ish on 2.4ghz and rest on 5ghz (AC,AX devices).  Looking at the logs it looks like for some reason every 12 hours a DHCP renewal happens. Weird that it is 12 hours even though 24 hours is what the router has set.

My theory became that every time the router is booted up or when the DHCP renewal happens, the RAX120 is hit with 20+ devices all renewing at the same time. I figure due to some reason the router might be trying to assign the same IP to 2 or more devices. This could be because the devices are MU-MIMO enabled and they are connecting too fast. Or it could be that this router has a quad-core and there is some race-condition when that many DHCP requests are coming in at the same time.

Whatever the case the only solution that seems to work right now is to reserve a bunch of IPs high up in the IP range for all of those devices that remain connected 24/7. When their DHCP leases due expired the server doesn’t struggle to provide a new lease and there is enough breathing room in the lower IP range for existing/new devices.

I really hope the firmware team takes a look at this post. They need to stress test use-cases such as this especially with devices getting faster and multiple connections possible at once (MU_MIMO and OFDMA).