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Blackhole DNS servers are DNS servers that return a "nonexistent address" answer to reverse DNS lookups for addresses reserved for private use. ==Background== RFC 1918 reserves several ranges of network addresses for use on private network in IPv4: * 10.0.0.0 – 10.255.255.255 * 172.16.0.0 – 172.31.255.255 * 192.168.0.0 – 192.168.255.255 Even though traffic to or from these addresses should never appear on the public Internet, it is not uncommon for such traffic to appear anyway. Some servers are configured (usually for logging reasons) to perform a reverse DNS lookup on clients' IP address. If the server encounters a packet originating from an RFC 1918 address, it may try performing such a lookup on that address. This causes unnecessary network traffic and may also impair the functionality of the server (because the query would go unanswered and the server would have to wait for the query to time out). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Blackhole server」の詳細全文を読む スポンサード リンク
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