[Dnsmasq-discuss] How to troubleshoot NXDOMAIN for local devices?

Discussion:

Todd Andrews

2018-02-15 22:05:33 UTC

Hi All,

I'm running dnsmasq 2.76 on a Raspberry Pi. It's been working great for
months but today I started seeing an odd behavior for a specific local
device and I don't know how to troubleshoot it.

The device is a Dell Inspiron 5577 Windows 10 Home edition laptop with the
latest Windows updates. It's getting an IP address of 192.168.1.115. I
first noticed the problem when I tried to establish a VNC connection to it
because I can't connect via its hostname, "sagan", but I can connect via
its IP address.

Neither the IP assignment nor the laptop's MAC address appear in
dnsmasq.leases. The only reason I know it is assigned .115 is by physically
going to the laptop and running the Windows 'ipconfig' program at the
command prompt.

I've rebooted the Raspberry Pi and the Windows 10 laptop, but it hasn't
made a difference.

More info below. Does anyone have any ideas?

Regards,
Todd

1. dnsmasq.log shows:

/var/log/dnsmasq.log:Feb 15 12:38:34 dnsmasq[738]: config 192.168.1.115 is
NXDOMAIN

2. I believe the following are the relevant dnsmasq config file entries.
These have been working for quite some time. I'm obfuscating the full MAC
address:

dhcp-host=f4:8e:38:xx:xx:xx,sagan

domain=si.loc
local=/si.loc/
expand-hosts

3. $ dnsmasq --test

dnsmasq: syntax check OK.

4. Using the program WinIPConfig2012 a.k.a. WinIPConfig 4.0
<http://www.pkostov.com/wordpress/?p=19>, I've verified that the laptop is
using the Raspberry Pi as the DHCP server. There's no other DHCP server on
my network that I know of.

5. On a third computer, a Macintosh, I get these results. The Raspberry Pi
is at 192.168.1.40.

$ ping sagan

*ping: cannot resolve sagan: Unknown host*

$ ping sagan.si.loc

*ping: cannot resolve sagan.si.loc: Unknown host*

$ dig sagan

; <<>> DiG 9.8.5-P1 <<>> sagan
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: *NOERROR*, id: 21157
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;sagan. IN A

;; Query time: 1 msec
;; SERVER: 192.168.1.40#53(192.168.1.40)
;; WHEN: Thu Feb 15 13:22:25 PST 2018
;; MSG SIZE rcvd: 23

$ dig sagan.si.loc

; <<>> DiG 9.8.5-P1 <<>> sagan.si.loc
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: *NXDOMAIN*, id: 11132
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;sagan.si.loc. IN A

;; Query time: 1 msec
;; SERVER: 192.168.1.40#53(192.168.1.40)
;; WHEN: Thu Feb 15 13:22:26 PST 2018
;; MSG SIZE rcvd: 30

$ nslookup sagan

Server: 192.168.1.40
Address: 192.168.1.40#53

Non-authoritative answer:
*** *Can't find sagan: No answer*

$ nslookup sagan.si.loc

Server: 192.168.1.40
Address: 192.168.1.40#53

** *server can't find sagan.si.loc: NXDOMAIN*

Andy Ruddock

2018-02-15 22:46:27 UTC

Permalink

Post by Todd Andrews
Hi All,
I'm running dnsmasq 2.76 on a Raspberry Pi. It's been working great for
months but today I started seeing an odd behavior for a specific local
device and I don't know how to troubleshoot it.
The device is a Dell Inspiron 5577 Windows 10 Home edition laptop with the
latest Windows updates. It's getting an IP address of 192.168.1.115. I
first noticed the problem when I tried to establish a VNC connection to it
because I can't connect via its hostname, "sagan", but I can connect via
its IP address.
Neither the IP assignment nor the laptop's MAC address appear in
dnsmasq.leases. The only reason I know it is assigned .115 is by physically
going to the laptop and running the Windows 'ipconfig' program at the
command prompt.
I've rebooted the Raspberry Pi and the Windows 10 laptop, but it hasn't
made a difference.
More info below. Does anyone have any ideas?
Regards,
Todd

Are you sure the windows box hasn't been configured with a static IP
address?

Any information when you refresh the IP address from within a cmd window
in Windows?
ipconfig /renew

Post by Todd Andrews
/var/log/dnsmasq.log:Feb 15 12:38:34 dnsmasq[738]: config 192.168.1.115 is
NXDOMAIN
2. I believe the following are the relevant dnsmasq config file entries.
These have been working for quite some time. I'm obfuscating the full MAC
dhcp-host=f4:8e:38:xx:xx:xx,sagan
domain=si.loc
local=/si.loc/
expand-hosts
3. $ dnsmasq --test
dnsmasq: syntax check OK.
4. Using the program WinIPConfig2012 a.k.a. WinIPConfig 4.0
<http://www.pkostov.com/wordpress/?p=19>, I've verified that the laptop is
using the Raspberry Pi as the DHCP server. There's no other DHCP server on
my network that I know of.
5. On a third computer, a Macintosh, I get these results. The Raspberry Pi
is at 192.168.1.40.
$ ping sagan
*ping: cannot resolve sagan: Unknown host*
$ ping sagan.si.loc
*ping: cannot resolve sagan.si.loc: Unknown host*
$ dig sagan
; <<>> DiG 9.8.5-P1 <<>> sagan
;; global options: +cmd
;; ->>HEADER<<- opcode: QUERY, status: *NOERROR*, id: 21157
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;sagan. IN A
;; Query time: 1 msec
;; SERVER: 192.168.1.40#53(192.168.1.40)
;; WHEN: Thu Feb 15 13:22:25 PST 2018
;; MSG SIZE rcvd: 23
$ dig sagan.si.loc
; <<>> DiG 9.8.5-P1 <<>> sagan.si.loc
;; global options: +cmd
;; ->>HEADER<<- opcode: QUERY, status: *NXDOMAIN*, id: 11132
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;sagan.si.loc. IN A
;; Query time: 1 msec
;; SERVER: 192.168.1.40#53(192.168.1.40)
;; WHEN: Thu Feb 15 13:22:26 PST 2018
;; MSG SIZE rcvd: 30
$ nslookup sagan
Server: 192.168.1.40
Address: 192.168.1.40#53
*** *Can't find sagan: No answer*
$ nslookup sagan.si.loc
Server: 192.168.1.40
Address: 192.168.1.40#53
** *server can't find sagan.si.loc: NXDOMAIN*
_______________________________________________
Dnsmasq-discuss mailing list
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

--
Andy Ruddock
------------
***@rainydayz.org (OpenPGP Key ID 0xB0324245)

Geert Stappers

2018-02-16 07:45:35 UTC

Permalink

Post by Andy Ruddock

Post by Todd Andrews
Hi All,
I'm running dnsmasq 2.76 on a Raspberry Pi.

FWIW there are 2.79 release candidates.

Post by Andy Ruddock

Post by Todd Andrews
It's been working great for
months but today I started seeing an odd behavior for a specific local
device and I don't know how to troubleshoot it.
The device is a Dell Inspiron 5577 Windows 10 Home edition laptop with the
latest Windows updates. It's getting an IP address of 192.168.1.115.

What did choose the .115 ??

Post by Andy Ruddock

Post by Todd Andrews
I first noticed the problem when I tried to establish a VNC connection to it
because I can't connect via its hostname, "sagan", but I can connect via
its IP address.

Is hostname "sagan" really configured inside the Windows 10 Home edition laptop??

Post by Andy Ruddock

Post by Todd Andrews
Neither the IP assignment nor the laptop's MAC address appear in
dnsmasq.leases. The only reason I know it is assigned .115 is by physically
going to the laptop and running the Windows 'ipconfig' program at the
command prompt.
I've rebooted the Raspberry Pi and the Windows 10 laptop, but it hasn't
made a difference.
More info below. Does anyone have any ideas?
Regards,
Todd

Are you sure the windows box hasn't been configured with a static IP
address?
Any information when you refresh the IP address from within a cmd window
in Windows?
ipconfig /renew

Post by Todd Andrews
/var/log/dnsmasq.log:Feb 15 12:38:34 dnsmasq[738]: config 192.168.1.115 is NXDOMAIN

Yes, that is problem original poster has.

Post by Andy Ruddock

Post by Todd Andrews
2. I believe the following are the relevant dnsmasq config file entries.
These have been working for quite some time. I'm obfuscating the full MAC
dhcp-host=f4:8e:38:xx:xx:xx,sagan

That is MAC-address and hostname.
Where is the "connection" / "link" with IP-address?

And about MAC-address:
* How many MAC addresses has the laptop?
* Are you using the right one?
* What was done to prevent typo errors?

Post by Andy Ruddock

Post by Todd Andrews
domain=si.loc
local=/si.loc/
expand-hosts
3. $ dnsmasq --test
dnsmasq: syntax check OK.
4. Using the program WinIPConfig2012 a.k.a. WinIPConfig 4.0
<http://www.pkostov.com/wordpress/?p=19>, I've verified that the laptop is
using the Raspberry Pi as the DHCP server. There's no other DHCP server on
my network that I know of.
5. On a third computer, a Macintosh, I get these results.

The third computer, what is the hostname?

Post by Andy Ruddock

Post by Todd Andrews
The Raspberry Pi is at 192.168.1.40.
$ ping sagan
*ping: cannot resolve sagan: Unknown host*
$ ping sagan.si.loc
*ping: cannot resolve sagan.si.loc: Unknown host*

Does it work for the hostname of the third computer?

Groeten
Geert Stappers

--
Leven en laten leven

Todd A

2018-02-16 17:03:02 UTC

Permalink

This post might be inappropriate. Click to display it.

Geert Stappers

2018-02-16 18:31:01 UTC

Permalink

Post by Todd A

Post by Todd Andrews
Hi All,
It's getting an IP address of 192.168.1.115. I
first noticed the problem when I tried to establish a VNC connection to it
because I can't connect via its hostname, "sagan", but I can
connect via its IP address.
Neither the IP assignment nor the laptop's MAC address appear in
dnsmasq.leases. The only reason I know it is assigned .115 is by physically
going to the laptop and running the Windows 'ipconfig' program at the
command prompt.
I've rebooted the Raspberry Pi and the Windows 10 laptop, but it
hasn't made a difference.
More info below. Does anyone have any ideas?
Regards,
Todd

Hi Andy, thanks for getting back to me so quickly. (I originally
sent this reply yesterday but forgot there's a maximum size per post
to this list. Replaced screen capture with a link below.)
Are you sure the windows box hasn't been configured with a static IP
address?
I'm positive: click to view screen capture <https://www.dropbox.com/s/cwy72yu4sly62mp/sagan-configured-as-dhcp.PNG?dl=0>
Any information when you refresh the IP address from within a cmd window
in Windows?
ipconfig /renew
I never would have thought to try this. It gave a strange error but
C:\Users\taa>ipconfig /renew
Windows IP Configuration
An error occurred while renewing interface Ethernet : The name
specified in the network control block (NCB) is in use on a remote
adapter.
The NCB is the data.
C:\Users\taa>
Having a specific error allowed me to Google it and find Bizarre
DHCP server error solved <https://web.archive.org/web/20161126203756/http://www.formortals.com/bizarre-dhcp-server-error-solved/>.
The poster at that link 1) was not getting an IP address at all, 2)
was running a Windows DHCP server, and 3) "found a second
reservation in DHCP which looked odd; it had the same IP address as
the first one that we deleted but it had an entirely different MAC
and name."
This made me remember that a couple of weeks ago I changed my
laptop's Computer Name in Windows.
Does this mean there is some other place where dnsmasq might have
cached the IP address or MAC or hostname? I'm trying to figure out
why dnsmasq.leases had no reference to the laptop's IP/MAC/hostname,
neither the previous hostname or the new one.

My guess would be
| dhcp-host=f4:8e:38:xx:xx:xx,sagan
as the original post mentioned. And assuming that dnsmasq is smart enough
to not log what is already documented in the (static) configuration.

Post by Todd A
Maybe this is one of those cases that is so bizarre
it defies explanation (and I can live with that). :D

I would culprit the host renaming.

Matching XKCD item at https://www.xkcd.com/910/ :-)

Groeten
Geert Stappers

--
Leven en laten leven

Todd Andrews

2018-02-16 17:32:45 UTC

Permalink

Hi Geert,