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While looking into mdns for an IOT device I was making I discovered that on my home network if I typed in hostname.lan, chrome browser would resolve the address to the appropriate local device with that hostname. When I ran nmap to scan for local devices it would also provide this information in the output

Example:

$: nmap -p 80 192.168.0.100

Nmap scan report for hostname.lan (192.168.0.100)
Host is up (0.00031s latency).
PORT   STATE SERVICE
80/tcp open  HTTP

I like this feature, but I am annoyed because it randomly stops for days at a time.

At first, I assumed this was something my router was doing (a TP-link Archer C9) but I have not been able to find a place to enable or disable this setting, nor any documentation about it on the internet. Then I thought maybe it was a program running on a raspberrypi, but have not been able to turn it on and off with any programs from my RPIs. I've spent a lot of time spinning my wheels searching the internet for what program makes the .lan domain, will very little luck.

My question is, how do I figure out who is resolving these addresses. Or in the sad situation where this never returns, how do I setup a DNS server that automatically resolves hostnames to IP addresses on my LAN?

jeffpkamp
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    Go to DOS. Type in nslookup hostname.lan and you know which DNS server responded https://en.wikipedia.org/wiki/Nslookup – Gantendo Apr 01 '22 at 18:29
  • Are you running PiHole on that RPI? You can enable a DNS server in PiHole. See also https://superuser.com/questions/45789/running-dns-locally-for-home-network and https://www.cloudsavvyit.com/14816/how-to-run-your-own-dns-server-on-your-local-network/ – Gantendo Apr 01 '22 at 18:34
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    mDNS is a zero-conf networking approach to name resolution, so the client sends a multicast request for a name to the whole LAN, and the station with that name responds, providing its IP, rather than using a centralized server. its likely that your router is using DNSMasq to forward queries up to your ISP DNS server for names that don't end in .local or .lan. check ipconfig /all to see what your configured DNS servers are, but I'm guessing it contains your routers IP address. your client will only use the DNS server IP if the name ends in a valid global TLD like .com/.edu/.gov/etc. – Frank Thomas Apr 01 '22 at 19:28
  • I've checked out all of your comments and the DNS is for normal webpage lookups is indeed going through my router, which I knew it was. However, since I've written this, the .lan resolution has stopped working :( and so I can't use nslookup to find it. Anyone know programs that perform this function? – jeffpkamp Apr 04 '22 at 14:59

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