@Malvazar 

Look at the IP information on the client devices to see what their DNS settings are at. You might need to manually set them up to point to the pi-hole.

^^^ That is what I do and it works.

@Malvazar You shouldn't need to point the secondary DNS slot on the DHCP server to the Pi-Hole IP, the Pi-Hole looks after the secondary DNS itself. It should work as you have configured it, with just the first DNS slot configured, but I configure each device (laptops, tablets, etc) seperately to point to the Pi-Hole DNS. I don't know if sometimes the DNS you enter on the DHCP can be overriden by your ISP's DNS IP address. 

@Malvazar 

The Router's WAN IP settings should use 1.1.1.1 or 8.8.8.8 or your carrier DNS info.

The PiHole (which I have setup as x.x.x.2 on my network, with x.x.x.1 being the router) IP information should only be listed in the LAN DHCP IP Settings.

Your router will always have good DNS information and won't use your PiHole, however your internal devices will grab DHCP from the router that contains the PiHole DNS info. So every device on your network uses the PiHole.

@Player911 

I have setup my TP Link Archer VR2800 router with two networks:

1. a local network, where all devices can talk to each other, and
2. a guest network (which I connect IoT devices), where I deliberately restrict devices from talking to the local network

The router acts as a DHCP server.

I have a DNS server that is on the local network (this is Pi-Hole). I have hard coded the router to DHCP announce the IP address of my local DNS server, x.x.x.254 (rather than use the default DNS details of my ISP).

While devices connected to the local network can access the local DNS server, devices connected to the guest network are unable to access the local DNS server - because I have disabled their LAN access. 

Is there a way I can have both local and guest networks access the local DNS server but NOT let devices on the guest network access the local network? Alternatively, am I able to offer a DHCP server which announces one set of DNS details to devices connected on the local network (i.e. the local devices use the IP address of my local DNS server for their DNS) and a different set of DNS details to devices connected to the guest network (i.e. guests use the IP address supplied by my ISP for their DNS)?

Thanks

E

@Els100 

Hello, 

I am having the same issue with TP-link M5 mesh modems.

I have manually set the Primary and Secondary DNS in the DHCP section to point to two pi-holes. The main home network works fine and can connect to the internet. The guest network is unable to connect to the internet. Only when I remove the Primary and Secondary DNS ip addresses does the guest network again connect to the internet.

As a temporary experiment I set the Primary and Secondary DNS in the IPv4 WAN section and both main and guest networks work fine and have internet access. I know and have confirmed that the modems have issues with that setup when power is cycled. The result for my M5's, in that situation when cycling power, is that they change the LAN IP from xxx.yyy.68.1 to xxx.yyy.0.1, and the DHCP start IP changs from xxx.yyy.68.100 to xxx.yyy.0.100 and the end IP from xxx.yyy.68.250 to xxx.yyy.0.250. The temporary experiment was removed, LAN IP reset and IPv4 WAN reset to automatic for normal operation.

So back to the original issue; How do I set up the M5 modems with a Primary and Secondary DNS in the DHCP section so that both the main and guest networks have internet access? 

Thanks