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Date: Wed, 07 May 2008 11:50:19 +0100
From: Christopher Key <cjk32@cam.ac.uk>
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Subject: Underscores in host names
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Hello,

I've a host on the network called "GC100_000C1E00AC3F_GlobalCache", and 
I'm getting interesting behaviour when I try to do DNS lookups on it.

Under FreeBSD, ping fails with 'Unknown server error'(distinct from the 
standard 'Unknown host'), and nslookup succeeds.  OSX and Windows 
machines will do a DNS lookup on it quite happily

The best explanation I can manage is that ping etc. are using different 
code from nslookup, and only nslookup is allowing the underscores within 
the hostname.

Is this behaviour by design?  My understanding is that underscores are 
not strictly permitted, but that most implementations choose to allow 
them unless there's a specific reason not to.


Regards,

Chris