Smartphone Identification Question

[djmcfar]

Have you looked at this thread:

Ubuntu 22.04 LTS Desktop - DHCP DNS servers ignored

Relatively new to linux and just needed to run through something: I've noticed that with Ubuntu 22.04 there is no way to disable the dns stub listener at install time nor run time on the live cd wi...

askubuntu.com

Interesting question posed by OP.

I started searching on whether Ubuntu intentionally blocks local name resolution, and it turns out that recent versions of dnsmasq do it on purpose, to supposedly thwart some bizarre attack type, so I uninstalled dnsmasq and did a cleanup, rebooted but the problem persists (additional paranoia somewhere in the convoluted network setup). I'm going to try to revert back to the old ifupdown style of networking (which is what was in place when I started with linux) and see if that fixes it. If it doesn't I'll turn the DHCP server back on, disable router DHCP and the get the info I'm looking for from the DHCP log file that I use. Maybe reverting back to 16.04 might be worth trying, IDK.

 

[drinkingbird]

Interesting question posed by OP.

I started searching on whether Ubuntu intentionally blocks local name resolution, and it turns out that recent versions of dnsmasq do it on purpose, to supposedly thwart some bizarre attack type, so I uninstalled dnsmasq and did a cleanup, rebooted but the problem persists (additional paranoia somewhere in the convoluted network setup). I'm going to try to revert back to the old ifupdown style of networking (which is what was in place when I started with linux) and see if that fixes it. If it doesn't I'll turn the DHCP server back on, disable router DHCP and the get the info I'm looking for from the DHCP log file that I use. Maybe reverting back to 16.04 might be worth trying, IDK.

That post seemed to imply it was DHCP learned DNS servers that were being ignored, have you tried statically setting the DNS server on the Ubuntu box to your router IP?

 

[djmcfar]

That post seemed to imply it was DHCP learned DNS servers that were being ignored, have you tried statically setting the DNS server on the Ubuntu box to your router IP?

No, I didn't try that. But it turns out that the root cause of the local DNS failures is beyond my control and has nothing to do with linux. I have VPN client enabled on the router and use the VPN Director rules to select VPN/WAN for the computers in the network. "Exclusive" mode was the only DNS setting that worked with all of the streaming services that we use, and unfortunately in exclusive mode there is no check for local DNS queries, so they get passed up-stream to the VPN's DNS servers who recognize it as a local network request and send the correct response, returning "localhost" as the authoritative nameserver and "not found" as the answer. If there was a check for local LAN queries, then the problem could be avoided. I'm going to start another question thread to RMerlin and see if he thinks that is possible for him to implement.

The thing that made me think of this as a possibility was nslookup failures from a new Windows 11 laptop that I never tried nslookup on until last night. The thing that me previously think is was a Linux issue, was I had servers running on the 3 windows boxes that I tried nslookup from (perforce and 2 web servers) and they were all set to use the WAN by VPN director rules, whereas the linux boxes were using the router's client VPN (along with the new windows laptop that failed nslookup).

I didn't think that this was possible, because sending a local src and dest DNS request upstream is guaranteed to fail. Now I feel stupid for blaming Linux (running and hiding) !!

Thanks again for your help with this issue. Cheers !!

 

[sfx2000]

.arpa is a reserved TLD, do not use it. Same with .local. That can cause you problems.

Just use "home" or "lan" or something like that.

recent guidance is that .home is being now used for matter/thread IoT...

https://www.ietf.org/archive/id/draft-tljd-dnssd-zone-discover-00.txt

.lan is becoming more popular these days for private in-house domain naming...

Of course, one could do home.lan, but one shouldn't do lan.home (see above)

 

[drinkingbird]

recent guidance is that .home is being now used for matter/thread IoT...

https://www.ietf.org/archive/id/draft-tljd-dnssd-zone-discover-00.txt

.lan is becoming more popular these days for private in-house domain naming...

Of course, one could do home.lan, but one shouldn't do lan.home (see above)

Yeah home.lan is my recommendation (for people who care, most average users don't know or care about LAN hostnames). Techically if you look at the spec there are only a few really dumb ones reserved for private use like .test and .debug.

Luckily I have my own domain and just use a subdomain of it for the LAN. If you specify nothing, I believe your ISP's domain will pass through, not sure if that is still the case though.

I'm just an old fart so having just hostname.lan looks wrong to me

Actually if you wanted to implement a crude parental control you could just use pornhub.com then nobody could ever get to that

 

[drinkingbird]

No, I didn't try that. But it turns out that the root cause of the local DNS failures is beyond my control and has nothing to do with linux. I have VPN client enabled on the router and use the VPN Director rules to select VPN/WAN for the computers in the network. "Exclusive" mode was the only DNS setting that worked with all of the streaming services that we use, and unfortunately in exclusive mode there is no check for local DNS queries, so they get passed up-stream to the VPN's DNS servers who recognize it as a local network request and send the correct response, returning "localhost" as the authoritative nameserver and "not found" as the answer. If there was a check for local LAN queries, then the problem could be avoided. I'm going to start another question thread to RMerlin and see if he thinks that is possible for him to implement.

The thing that made me think of this as a possibility was nslookup failures from a new Windows 11 laptop that I never tried nslookup on until last night. The thing that me previously think is was a Linux issue, was I had servers running on the 3 windows boxes that I tried nslookup from (perforce and 2 web servers) and they were all set to use the WAN by VPN director rules, whereas the linux boxes were using the router's client VPN (along with the new windows laptop that failed nslookup).

I didn't think that this was possible, because sending a local src and dest DNS request upstream is guaranteed to fail. Now I feel stupid for blaming Linux (running and hiding) !!

Thanks again for your help with this issue. Cheers !!

If your linux box or raspberry pi etc is up all the time, could just move DNS and DHCP to there.

 

[sfx2000]

I'm just an old fart so having just hostname.lan looks wrong to me

I'm an equally old fahrt, and .lan as a tld for a local network is just fine...

I am the maintainer here for the reserved parametric FAQ - if you have inputs, happy to add them...

FAQ - Reserved Characters/Names - SSID/Passwords/Hostnames/Domains

Maintaining/updating this list - I've tried to capture most of the characters/words/ranges to avoid - if there are more, please reply to this thread and I'll update the list... Changelist 08/9/22 - update for Thread IOT reserved HLD's (.home, .service) 08/11/19 - quick update about reserved...

www.snbforums.com

 

[drinkingbird]

I'm an equally old fahrt, and .lan as a tld for a local network is just fine...

I am the maintainer here for the reserved parametric FAQ - if you have inputs, happy to add them...

FAQ - Reserved Characters/Names - SSID/Passwords/Hostnames/Domains

Maintaining/updating this list - I've tried to capture most of the characters/words/ranges to avoid - if there are more, please reply to this thread and I'll update the list... Changelist 08/9/22 - update for Thread IOT reserved HLD's (.home, .service) 08/11/19 - quick update about reserved...

www.snbforums.com

Nah I just mean not having a domain along with the TLD. Of course it works perfectly fine and is perfectly valid I am just set in my ways.

 

[drinkingbird]

I'm an equally old fahrt, and .lan as a tld for a local network is just fine...

I am the maintainer here for the reserved parametric FAQ - if you have inputs, happy to add them...

FAQ - Reserved Characters/Names - SSID/Passwords/Hostnames/Domains

Maintaining/updating this list - I've tried to capture most of the characters/words/ranges to avoid - if there are more, please reply to this thread and I'll update the list... Changelist 08/9/22 - update for Thread IOT reserved HLD's (.home, .service) 08/11/19 - quick update about reserved...

www.snbforums.com

Heh looking at your list reminds me of my first network engineer job out of college long ago where they had thousands of hostnames in their internal DNS using underscore, it was actually a documented naming standard. It worked for the most part but several things did have issues with it. BIND surprisingly didn't care, nor did the IP management system they were using. But engineers peer review each others work and I'd always reject when I saw they had assigned a hostname with _ in it. I became the "underscore nazi".

 

[ColinTaylor]

If you specify nothing, I believe your ISP's domain will pass through, not sure if that is still the case though.

That's not the case with Asus routers.

 

[thecheapseats]

Heh looking at your list reminds me of my first network engineer job out of college <snip>

the chronology sieve of old fahrt is the proper application of the number of obsoleted RFCs at the time you were first allowed to touch stuff and get paid for it -or if you prefer - naming conventions that didn't break sed or awk... you choose... mine goes back to pre-iana when postel hired me as an indentured janitor... it was close to the beach - so I didn't care...