Can Not ping Hosts by name when Underscores are Present.

[Charles Swiger]

On Mar 3, 2004, at 12:56 PM, Martin McCormick wrote:
> 	Does the ping utility do some sort of name checking when one
> wants to ping a particular host by name?

Ping uses gethostbyname2() to resolve the target hostname.

> 	A person with an account on a FreeBSD system demonstrated to
> me that one could successfully look up a given host using nslookup but
> if you pinged that host by name as in
>
> ping host_name.domain, one got an immediate complaint from the ping
> utility like:
>
> ping: cannot resolve cl_mail1.mydomain: Unknown server error

That sounds about right.  nslookup is a testing utility which allows 
one to query RRs for string you want, including ones which correspond 
to invalid hostnames.

The underscore is not allowed in Internet hostnames-- see RFC-952 and 
-1123.

-- 
-Chuck