Peculiar LAN name resolution issue

sbsnb

Very Senior Member
Need I say more?

Code:
C:\>nslookup 192.168.1.43
Server:  RT-AX86U-AA38.foo.lan
Address:  192.168.1.1

Name:    bar
Address:  192.168.1.43


C:\>nslookup bar
Server:  RT-AX86U-AA38.foo.lan
Address:  192.168.1.1

*** RT-AX86U-AA38.foo.lan can't find bar: Non-existent domain
 

sbsnb

Very Senior Member
I haven't done anything except this line in /jffs/configs/dnsmasq.conf.add:

Code:
dhcp-host=DE:AD:BE:EF:CA:FE,bar,192.168.1.43,12h

It is also named in NVRAM:

Code:
custom_clientlist=<bar>DE:AD:BE:EF:CA:FE>0>0>>
 

ColinTaylor

Part of the Furniture
Has the client with MAC address DE:AD:BE:EF:CA:FE connected to the router via DHCP? If not the dhcp-host line will not have been activated.

The custom_clientlist does not affect DNS.
 

sbsnb

Very Senior Member
That first I thought you had it. The client has been up for 544 days, but the router has only been up for 216 days. However, this problem isn't unique to this client. All clients on my LAN have the same issue. The only strange thing about the "bar" client is that reverse DNS works, where it does not for other clients.
 

ColinTaylor

Part of the Furniture
The only strange thing about the "bar" client is that reverse DNS works, where it does not for other clients.
Yes that's what I can't figure out. Not being able to resolve host "bar" is to be expected, but I don't understand why "192.168.1.43" is resolving to a domain name called "bar".
 
Last edited:

RMerlin

Asuswrt-Merlin dev
Try using the FQDN instead:

Code:
nslookup foo.bar.lan

If it still fails, then probably your router doesn't have any DNS entry for that hostname, and what the Windows nslookup is doing is resolving the IP through a different method than a DNS query.
 

torch

Occasional Visitor
As I understand it, nslookup has its own code for resolving IP addr/hostname and does not use the underlying operating system's (Linux, Windows, MacOS) code.
 

RMerlin

Asuswrt-Merlin dev
As I understand it, nslookup has its own code for resolving IP addr/hostname and does not use the underlying operating system's (Linux, Windows, MacOS) code.
Being a Microsoft tool, only Microsoft truly knows what is going on under the hood. :)
 

sbsnb

Very Senior Member
Well how does one go about making local LAN name resolution work? It doesn't work from any LAN device (Windows, Mac, Android). I didn't used to have any problem.
 

ColinTaylor

Part of the Furniture
I didn't used to have any problem.
You've reported multiple DNS related issues this year. It seems likely this is just a continuation of those. Did you ever do the factory reset that was suggested back then?


For the specific Windows output in post #1, your PC doesn't appear to have a Connection-specific DNS Suffix set. I'm guessing this is because your router's DNS was not configured correctly the last time this PC was restarted. I suspect that if you reboot that PC now it might work correctly.
 
Last edited:

drinkingbird

Very Senior Member
Well how does one go about making local LAN name resolution work? It doesn't work from any LAN device (Windows, Mac, Android). I didn't used to have any problem.

The only way to get something into DNS on the Asus router is to create a static DHCP reservation for it and make sure the router knows it is active (i.e. bounce the device so it pulls a lease). You can manually add stuff to dnsmasq too if you want to do scripts etc, but if you're going to do that, you need to give the device a static IP, so might as well just use DHCP reservation for that.

Whatever is shown in the client list will have no impact on DNS, only the hostname in the DHCP bindings table will be in DNS.

Why it has a PTR record but not an A record who knows, maybe you created one while toying around or maybe it is left over from when it did have a good DNS entry for the device.
 

sbsnb

Very Senior Member
You've reported multiple DNS related issues this year. It seems likely this is just a continuation of those. Did you ever do the factory reset that was suggested back then?

No. Those issues are unrelated. The problem resolving the sce.com domain was related to the specific DNS server I was using. The intermittent DNS failures happen when using stubby or dnscrypt regardless of how many resets I do.

For the specific Windows output in post #1, your PC doesn't appear to have a Connection-specific DNS Suffix set. I'm guessing this is because your router's DNS was not configured correctly the last time this PC was restarted. I suspect that if you reboot that PC now it might work correctly.
It's not Windows, specific. Reboot doesn't fix it. All devices on the LAN have the same issue.
 

sbsnb

Very Senior Member
You even made me boot up a Linux Mint live USB. Still same problem.

Code:
$ nslookup 192.168.1.43
43.1.168.192.in-addr.arpa    name = bar.

Authoritative answers can be found from:

$ nslookup bar
Server:        127.0.0.53
Address:    127.0.0.53#53

** server can't find bar: SERVFAIL
 

sbsnb

Very Senior Member
Code:
$ dig bar

; <<>> DiG 9.16.1-Ubuntu <<>> bar
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 18086
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;bar.            IN    A

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Wed Nov 02 15:35:24 PDT 2022
;; MSG SIZE  rcvd: 40
 

sbsnb

Very Senior Member
FQDN doesn't help.

Code:
$ dig bar.foo.lan

; <<>> DiG 9.16.1-Ubuntu <<>> bar.foo.lan
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 65052
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;bar.foo.lan.    IN    A

;; Query time: 496 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Wed Nov 02 15:40:53 PDT 2022
;; MSG SIZE  rcvd: 55

Code:
$ nslookup bar.foo.lan
Server:        127.0.0.53
Address:    127.0.0.53#53

** server can't find bar.foo.lan: NXDOMAIN
 
Last edited:

ColinTaylor

Part of the Furniture
Rich (BB code):
$ nslookup 192.168.1.43
43.1.168.192.in-addr.arpa    name = bar.

Authoritative answers can be found from:
That appears to be the same problem that I mentioned for Windows. Notice that the name returned is "bar." when it should be "bar.foo.lan.". This suggests to me that the domain isn't set correctly on either the router or the clients.

Code:
$ nslookup bar
Server:        127.0.0.53
Address:    127.0.0.53#53

** server can't find bar: SERVFAIL
Try doing this instead:
Code:
nslookup bar.
or this
Code:
nslookup bar. 192.168.1.1
 
Last edited:

sbsnb

Very Senior Member
Code:
$ nslookup bar.
Server:        127.0.0.53
Address:    127.0.0.53#53

** server can't find bar: SERVFAIL

$ nslookup bar. 192.168.1.1
Server:        192.168.1.1
Address:    192.168.1.1#53

Name:    bar
Address: 192.168.1.43
 

ColinTaylor

Part of the Furniture
As a sanity check can you post the output of this command run on your router:
Code:
egrep "domain|local" /etc/dnsmasq.conf
 

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