Can't resolve a domain by Cache Server

[Joe Shen]

Hi,

We met a strange behavior with our cache server that
it can't resolve a special domain from time to time. 

The phenomenon is: we set up a cache server on a
Solaris8 with BIND9. It seems it could serve our
customers' requestes successfully. But, the day before
yesterday someone told me the cache server could not
resolve names under 50hz.cn from time to time. 

We check ns1.50hz.cn , ns2.50hz.cn, www.50hz.cn by
nslookup. The results shows , the three names could be
solved from time to time but it fails frequently.
There is no periodical characteristics with the
frequency of failings.  If we set up cache server to
forward all requests on 50hz.cn to its name server, no
requests fails.  We contacted with administrator of
50hz.cn and they told us they use BIND9 on Linux .
We don't understand why this happens and how could we
fix it.

Has anybody met similar problem? 

Thanks.

Joe 

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