Cannot NSLOOKUP a server on wired LAN

[JDMils]

When I connect my Surface Pro to the Google Nest WiFi, I cannot ping my server DOWNLOADS via its DNS name but I can PING the server by IP. This server is a virtual server running on my Synology NAS. I can PING the DOWNLOADS server via DNS from my LAN or from my Telstra home router's WiFi. So I guess I have a DNS issue wrt this server.

I cannot ping any devices on the Home router's LAN or WiFi using DNS, only IP.

So how do I set all devices which connect to my Google Nest WiFi to use my router (10.0.0.250) DNS server?

I have the Google Nest WiFi router H2D.

[MichaelP]

Hello @JDMils 

I suspect this may be caused by how you have devices all connected. It sounds like you have a Telstra combination modem+router+firewall+WiFi unit to provide internet service. Since it's more than just a modem, it's also creating a new private network.

Then, you also have a Nest WiFi Router unit connected via Ethernet to that Telstra unit. The Nest WiFi Router is also a router+firewall+WiFi, so it is creating another "inner" private network, inside the "outer" network created by your Telstra device.

Communications between these two networks are limited by the firewall function in the Nest WiFi Router unit. DNS resolution is also impacted, but in ways that are somewhat complex – and only applicable for devices on that "outer" network. What happens is, any device doing a DNS lookup on the inner (Nest WiFi) network will send their DNS request to the Nest WiFi Router unit, which tries to resolve the address on either the inner network it created, or (for typical domain names ending in things like .com or .org, for example) sends the request straight out to an internet DNS server. It may not send it to the DNS server on the Telstra unit.

So, there is one quick thing you can try: adjust the DNS server settings on the Nest WiFi Router to configure it to send external DNS requests to your Telstra unit instead of "Automatic" (which, I believe, sends them directly to Google's DNS servers). This is a bit of a shot in the dark, though – I have no idea if it will work, and there's a chance it will cause problems for your Nest WiFi system (worst case, requiring a reset).

However, the best solution here is to make sure all devices are connected to the same network without a firewall in between them. That means having your Nest WiFi Router be the only thing directly connected to your Telstra unit, having the Telstra unit's WiFi disabled or at least set to a different SSID (network name), and then connecting all of your wired devices through a switched Ethernet network to the LAN Ethernet port on the Nest WiFi Router unit.

[JDMils]

Thanks for the informative write-up. Unfortunately it seems that the DNS settings on the Google WiFi router are not for DHCP but for the Google router itself. I set DNS to Custom and to point to my Telstra router however when the notebook on the Google Nest WiFi, I get the following:

Wireless LAN adapter Wi-Fi:

   Connection-specific DNS Suffix  . : lan
   Description . . . . . . . . . . . : Intel(R) Wi-Fi 6 AX201 160MHz
   Physical Address. . . . . . . . . : 5C-87-9C-D5-7F-D7
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 192.168.86.56(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Tuesday, 23 April 2024 9:31:08 PM
   Lease Expires . . . . . . . . . . : Wednesday, 24 April 2024 9:33:18 PM
   Default Gateway . . . . . . . . . : 192.168.86.1
   DHCP Server . . . . . . . . . . . : 192.168.86.1
   DNS Servers . . . . . . . . . . . : 192.168.86.1
   NetBIOS over Tcpip. . . . . . . . : Enabled

192.168.86.1 is the Google Router. Does not seem to be a way to set DHCP DNS for clients.

The only other thing I can think of is to create a DNS server on the 10.0.0.x Telstra LAN and point the Google Nest Router to it and see what happens.

Is there a way to set DNS for DHCP clients on the Google router?

[MichaelP]

The Nest WiFi Router unit configures clients on its inner network to use itself as the DNS server (for a couple reasons, including the ".lan" domain resolution for devices on that network, but also as part of the "safe search" feature). You can configure it to use any other IP address you want it to forward requests to, though.

It's not clear how DNS resolution is working on the outer network created by your Telstra router. If you're using mDNS (the ".local" domain), then that's done using link-local multicast, not an actual DNS server. It won't work through a router.

In any case, trying to run two different networks, with one inside the other one is always going to introduce complex connectivity and name resolution issues. That's why my earlier advice was to put everything on the same inner network created by Nest WiFi. Ideally, you'd then put the Telstra router in bridge mode to eliminate the resulting double NAT, but for many people, that isn't critical.

[JDMils]

Interestingly I removed the secondary DNS setting 8.8.8.8 and the internet stopped working on the notebook connected to the Google Router. I set the secondary DNS back to 8.8.8.8 and the internet is working OK. I changed the primary DNS to a non-existent IP such as 10.0.0.25 and the internet is still working OK.

Seems my Telstra router is not working as a DNS server for the Google router.

If I change the notebook to the Telstra router WiFi everything inside & outside is working OK.

Strange!

[JDMils]

I think you are correct that I have a double-NAT situation. I found one solution: I created a DNS server on my Synology NAS and manually created records for the devices on the Telstra router LAN, set the Google router to forward to the Synology NAS then the Google mesh clients can resolve DNS for the Telstra router clients. It's not ideal, as I have to use the Synology NAS as a DNS server and I have to manually create DNS records for the Telstra LAN devices I want to access from the Google mesh LAN.

The Telstra router (DJA0231) does not allow DNS server IP to be specified in DHCP settings. I may have to move DHCP to the Synology NAS as well.