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As the sketch suggests, I'm trying to design a home network using a Mac mini as a DNS and DHCP server. My idea is to have the ISP router only act as Gateway to the internet. Since the Mac mini only has one ethernet connection, I was thinking to put a switch between the ISP router and Mac + Ubiquiti AP.

My question is, could a configuration like the above work? Or would I require some other configuration? I do not want the wireless devices to get IPs from the ISP router. I have disabled the Wifi on that one as well. How can I make sure that the AP hands out IPs on the Mac's subnet and not on the ISP router's subnet?

Thanks in advance!

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  • Where is the gateway between 192.168.0.0/24 and 192.168.10.0/24 in your diagram?
    – u1686_grawity
    Mar 2, 2021 at 19:37
  • @user1686 I guess that would be the switch? Or does it not count as a gateway?
    – Phil
    Mar 2, 2021 at 20:36
  • No, it doesn't. It's a switch; only routers are "gateways". In your diagram, either you have only one subnet (with only the ISP router as the gateway and the Mac only issuing IP addresses), or you have two subnets sharing the same Ethernet (i.e. sharing the broadcast domain) with probably the Mac additionally acting as a gateway between the two. I'd suggest going with the former, for performance and for simplicity.
    – u1686_grawity
    Mar 2, 2021 at 21:19
  • Oh I see. So if I want two subnets (which I want), I will need to either get another router or set up two "virtual" subnets via the same ethernet interface on the Mac? I've been using computers for 25 years and been a developer for many years also but somehow with networking I have so many holes in my fundamental knowledge...
    – Phil
    Mar 3, 2021 at 7:54
  • Yes. Though it depends on how fast you need your Internet access to be. (While a "router on a stick" configuration with both subnets on a single Ethernet port could technically handle 1 Gbps sum(upload+download) -- i.e. 1 Gbps up, or 1 Gbps down, or 500 Mbps simultaneous up+down, etc. -- I'm not sure whether your Mac is powerful enough, and to be honest I'm not sure if macOS is suitable for routers either.) If it at least had two Ethernet ports (non-USB) and ran a Linux or a BSD, that would've been a bit better. But in your case I would say use a dedicated router instead.
    – u1686_grawity
    Mar 3, 2021 at 8:02

1 Answer 1

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You need to deactivate the DHCP Server on the ISP router. There can't be two DHCP servers on the same LAN/WLAN. This is unless you can configure the switch not to "forward" DHCP packages to your ISP router (which usually can not be done on consumer switches).

Make sure that your ISP router is in the subnet as the MAC mini! If they are not in the same subnet your MAC mini will need routing functionality.

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  • Ok! I can do that. Would you recommend another configuration though? Thanks!
    – Phil
    Mar 2, 2021 at 20:38
  • @Phil Your ISP router must be in the subnet as the MAC mini, other then that it's fine.
    – Albin
    Mar 2, 2021 at 20:41
  • BTW, of course there can be more than one DHCP server on the sam LAN/WLAN...but must be well designed and is usually done in larger environments for failover see example here Microsoft - Step-by-Step: Configure DHCP for Failover
    – Zina
    Mar 2, 2021 at 22:19
  • @Zina I was talking about the OP's scenario, not in absolute terms... according to his/her intentions and the way he configured the two DHCP servers I stand by my statement.
    – Albin
    Mar 3, 2021 at 0:08
  • Thanks! Regarding the subnet though, when you say the Mac mini will need routing functionality, what do you mean specifically? Some special software I need to get or some configuration in Mac OS? If it's not a hardware limitation I think I'l be able to figure it out.
    – Phil
    Mar 3, 2021 at 7:59

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