# Minor annoyance (do Tesla software engineers not know the detailes of DNS?)



## SimonMatthews (Apr 20, 2018)

Whenever my car connects to my WiFi, it creates this message in my log files because of the dynamic DNS that runs on my home network (*):


> Jul 12 16:55:52 myserver named[5861]: zone <my network>/IN: Tesla_Model_3.home.<my network>A: bad owner name (check-names)


DNS doesn't allow underscores in names. Do Tesla's engineers not know this?

*I have replaced the actual network name with "<my network>".


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## Klaus-rf (Mar 6, 2019)

While underscores are not allowed in *domain names*, they are allowed in subdomain and host names.


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## garsh (Apr 4, 2016)

Klaus-rf said:


> While underscores are not allowed in *domain names*, they are allowed in subdomain and host names.


I don't think that's true. It certainly never used to be true, but I'm trying to hunt down if/when that was changed.

RFC 952 - hostnames had to start with a letter and could only contain letters, numbers, and hyphens.
RFC 1123 - allowed hostnames to begin with a number.
RFC 2181 - clarifies that it's not DNS imposing such restrictions. DNS itself allows arbitrary byte strings as labels.

Ok, here we go:
https://en.wikipedia.org/wiki/Hostname
_Notwithstanding the standard, Chrome, Firefox, Internet Explorer, Edge and Safari allow underscores in hostnames..._​_However, it is valid to attempt to resolve a hostname that consists of an underscore. E.g. _.example.com._​
So no, hostnames should not contain underscores. But it appears that many parties ignore this rule, so modern routers should probably accept and work with such names.


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## Klaus-rf (Mar 6, 2019)

Time to call the RFC Police and tell them people are doing it wrong and the Internet is broken!!??


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## lance.bailey (Apr 1, 2019)

people still doing underscores? I remember running up against this in 1994 when the Mac resolver libraries refused to use any IN record containing an underscore (sunOS was fine, PC-NFS on windows was fine). Annoying when I looked up the RFC docs and found that Apple was actually doing it right 

I am wondering who generated the underscores - the offending record mentions "Tesla_Model_3.home.<my network>" - would "Tesla_Model_3" not come from your name for the car? Is Tesla replacing spaces with underscores and creating the error?


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## SimonMatthews (Apr 20, 2018)

I suspect that "Tesla_Model_3" is a default that is built into the cars. It's actually a poor default: they should really make the name unique somehow (pull the VIN?). 

I know that this is not what I have called my car and I have not configured it anywhere. I just checked the WiFI settings and did not see any way to configure this. It's not the name that I have given to my car.


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## mrau (Nov 22, 2018)

My car has the same name, "Tesla_Model_3" on WiFi. Don't know how or if it can be changed.


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