Network error while opeing Central Administration

Hi all,

  While opening my central Administration i am getting below error


Network Error (dns_server_failure)

 
Your request could not be processed because an error occurred contacting the DNS server. 
The DNS server may be temporarily unavailable, or there could be a network problem. 

For assistance, contact your network support team. 


Actually my Central Admin url is "http://microsoft-02:21673/default.aspx "

But when i browse the site by IP its opens fine without any error(http://myIPhere:21673/default.aspx)

Even after creating the site, i am unable to browse it with the machine name(http://microsoft-02:8090/default.aspx)
What Could be cause for this. Can anyone please suggest me what could be wrong

Thanks in advance
Resh

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Regards Reshma