Did anyone solve the Catalina DHCP problem?

Well, I figured it out. It was not Catalina and it was not my new eero. It was my **** Ooma hub. Turns out it likes to play DHCP, too. My fault as I had it installed backward after my eero installation. I pulled it for now, and everything appears to be working.

It’s odd, though, that the only device to register an address off the Ooma was my laptop, though. I have dozens of devices on my network and yet it was only the MacBook that acted up. I’ll have to do more research on DHCP protocols to discover that idiosyncrasy.

Apparently, it’s worse than I thought.

My MacBook is taking over as a DHCP server. Even after manually configuring it’s IP address, it still is pushing the wrong IP addresses to devices that come up on my network. I started a different device while my MacBook was on but inactive, and it was given a bad IP address (172 vice 192). I was not able to get the other device to renew with a good IP until after I shutdown the MacBook completely.

This is unacceptable! I cannot just manually configure IP addresses for every device I add to the network. That would be silly.

Does anyone have any suggestions? I am not familiar enough with MacOS to know how to prevent it from acting as the DHCP server.

That’s not true. The role of DHCP can be done by any device behind the router, as long as it provides the proper gateway and DNS servers. You are thinking of the actual NAT; that can only be done by a router.

You can also have a closed network with no Internet access, and no routers to other networks, still with DCHP allocating addresses. This is what commonly happens when a computer implements Layer 3 protocols without discovering a DHCP. It assigns itself an address, mask, and gateway like it is the DHCP server. What I hadn’t expected was my MacBook running Catalina to also *advertise* as a DHCP to other devices on my network. I might expect this when I connect two computers together without any other network devices between. I just do not expect this when there is already a device (the router) acting as the DHCP server on anetwork.

So, my guess is either Catalina is not seeing the existing DHCP service, or its ignoring it. Since the MacBook is successfully advertising as another DHCP on my network, and since it can access the Internet when it is manually configured, it points to good hardware and good Layer 2 connectivity (which is WiFi in my case, by the way.)

I am a network guy. I know that side. I just do not know MacOS.

BobTheFisherman wrote:

PJMayo said "That’s not true. "

OK, tell us what the solution is then.

I was responding to the statement from your previous post,

The only way your computer would act as a DHCP server is if you were sharing its Internet connection with a connecting device.

That statement was not true. Your statement about DHCP being only available through a routing or bridging device was not technically correct. Your link to configuring Computer Sharing was good, but was not applicable in my case.

If I had a solution, I would not have posted the question.

Erik Hess wrote:

My connectivity was restored (at least for now) by enabling IPv6 on my Eero network under Settings > Advanced in the iOS Eero app. It required a network reboot.

That worked for me, as well, but it does not explain why MacOS is requiring an IPv6 presence to configure IPv4 DHCP. I will have to research IPv6/DHCP interactions. I notice that I am unable to disable IPv6 on the MacBook. All my networks are IPv4, so I have never had to expand my knowledge of IPv6. I guess I will have to rectify that since it appears Apple intends IPv6 to be always up and running. lol

My satellite eero (another Pro) disconnected from my network after trying to turn IPv6 off again. I had to reset and reinstall it to restore it. I don’t know if that is an eero bug or another conflict that snuck up with the MacBook. It rebuilt fine. I did this with IPv6 turned back on.

My MacBook does appear to no longer be trying to provide IPv4 addresses. I still had it on when I re-registered the second eero device, but I also had the IPv6 active.

Turning on IPv6 on the router has definitely led to a solution for now. I’ll turn on my iMac next and see what happens.

As an aside, the MacBook was still getting a good IPv4 address when I tried turning IPv6 off again on the eero, so woodmeister50 may have a point about a rebuilt profile having an impact. I won’t know for sure until I do a little more experimenting. If I cannot recreate the original symptoms, I’ll have to assume a corrupt profile might have been the original problem.

I’m done experimenting for now. It is time for sleep. 😏

I checked the Internet Sharing option. It is disabled.

Looks like the IPv6 fix was not enough. I just turned on my MacBook and it’s using a 172.27 address again. Very frustrating!