WLAN on different subnet to LAN: How to get name resolution from LAN DNS servers?

BlizzardX · 24 Jan 2018 at 23:20

Hi

I'm new to this networking malarky with subnets and vlans etc. I've just replaced all my network gear with Ubiquiti Unifi (USG, AP-AC-LR & 24 switch) and have utilised the second LAN port on the USG for the AP.

As the USG Lan 2 port is a routable port and not switchable, i needed to set up a new subnet to get it to work... This works fine and devices connected can see the internet as well as ping devices on the LAN, but what I can't get working is name resolution.

Pinging 192.168.1.3 returns fine, but pinging dc1 errors out; for reference DC1 is a AD/DNS/DHCP server on 192.168.1.3.

The WLAN exists on 192.168.2.0/24 with the main lan on 192.168.1.0/24.

Is it possible to 'bridge' the DNS/DHCP server across the subnets and then avoid the USG dishing out DHCP on WLAN subnet?

Thanks

Chris

BlizzardX · 24 Jan 2018 at 23:36

So for the options on the USG allow me to setup a DHCP server, relay or none... I've tried the relay options but the devices lose their IPs which suggests that the DNS / DHCP servers on the LAN subnet haven't been routed, or cannot route. The routing options of the USG have entries for the LAN>WLAN and WLAN > LAN with the interface set rather than next hop.

I'm not sure how to change which DNS server it uses.

BlizzardX · 24 Jan 2018 at 23:53

DC1 is the DNS server (along with DC2) for LAN (192.168.1.0/24). WLAN subnet doesn't have a dedicated DNS server attached and is getting its IP address from the USG DHCP server, which is probably the google dns, and this clearly won't resolve private names I guess what I need the Unifi USG to do is allow me to specify a DNS server in its DHCP or even better allow me to relay the DHCP from the LAN subnet to the WLAN subnet.

As you can tell I am really new to networking at this sort of simple complexity

edit: ipconfig /all on the laptop shows DNS servers to be 192.168.2.1 which is the subnet gateway for the USG

BlizzardX · 25 Jan 2018 at 00:42

Right so I'm an idiot.

Clearly the subnet routing was working fine as I was able to ping ok, what I had missed was the ability to set a custom DNS server. Shifting those over to my DNS servers now does name resolution... Stupid!

Question though, is it possible to create a new scope in Windows DHCP for the new subnet; so I'll have a DHCP scope for LAN and a DHCP scope for WLAN? If so, with the routing setup that means that I can assign DHCP settings across my network from the same servers rather than a device?