Site with underscore at the end of 4th level domain name can’t be reached

We have our devel server in our company. Since 2006 we have this rule – if the project is finished and moved to production we have to append an underscore to the project name in the filesystem. So the url is changed from

projectname.devel.domain.tld

projectname_.devel.domain.tdl

I’m a linux user since 2008 but I was never able to open this site. It can’t be reached. I know this is working from windows but why is it not working from linux? Is it problem with DNS? I use DNSmasq for 4 years only without any change of behaviour to these project domains.

Traceroute to regular project name

    $ traceroute projectname.devel.domain.tld
    traceroute to projectname.devel.domain.tld (x.x.x.x), 30 hops max, 60 byte packets
     1  gateway (192.168.1.1)  1.815 ms  1.801 ms  1.798 ms
     2  ttxf1.ttx-net.sk (x.x.x.x)  3.823 ms  3.792 ms  3.742 ms
     3  ttx00.ttx-net.sk (193.110.186.1)  4.441 ms  3.774 ms  4.432 ms
     4  10.100.101.158 (10.100.101.158)  15.013 ms  15.026 ms  15.017 ms
     5  10.100.109.29 (10.100.109.29)  14.995 ms  15.003 ms  14.978 ms
     6  10.100.103.9 (10.100.103.9)  15.634 ms  11.021 ms  10.978 ms
     7  10.100.100.1 (10.100.100.1)  10.896 ms  5.784 ms  5.646 ms
     8  * * *
     9  * * *
...
    28  * * *
    29  * * *
    30  * * *

traceroute to projectname with underscore

$ traceroute projectname_.devel.domain.tld
projectname_.devel.domain.tld: Name or service not known
Cannot handle "host" cmdline arg `projectname_.devel.domain.tld' on position 1 (argc 1)

Any clue? Thanks

Answer

Because it is not compliant with the RFCs to have an underscore at the beginning or ending of a public hostname. Linux adheres to this, Windows does not.

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Answer