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[DNS] 请教一个DNS问题 [复制链接]

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发表于 2006-11-07 10:46 |显示全部楼层
在递归查询时能能否使用forwarding

应该怎么配置

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发表于 2006-11-08 07:50 |显示全部楼层
各位知道的大哥说句话啊

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发表于 2006-11-09 10:15 |显示全部楼层
The following texts were quoted from Bv9ARM.pdf

1.4.5    Caching Name Servers
The resolver libraries provided by most operating systems are stub resolvers, meaning that they are not
capable of performing the full DNS resolution process by themselves by talking directly to the authori-
tative servers. Instead, they rely on a local name server to perform the resolution on their behalf. Such
a server is called a recursive name server; it performs recursive lookups for local clients.
To improve performance, recursive servers cache the results of the lookups they perform. Since the
processes of recursion and caching are intimately connected, the terms recursive server and caching server
are often used synonymously.
The length of time for which a record may be retained in in the cache of a caching name server is
controlled by the Time To Live (TTL) field associated with each resource record.

1.4.5.1   Forwarding
Even a caching name server does not necessarily perform the complete recursive lookup itself. Instead,
it can forward some or all of the queries that it cannot satisfy from its cache to another caching name
server, commonly referred to as a forwarder.
There may be one or more forwarders, and they are queried in turn until the list is exhausted or an
answer is found. Forwarders are typically used when you do not wish all the servers at a given site
to interact directly with the rest of the Internet servers. A typical scenario would involve a number
of internal DNS servers and an Internet firewall. Servers unable to pass packets through the firewall
would forward to the server that can do it, and that server would query the Internet DNS servers on the
internal server’s behalf. An added benefit of using the forwarding feature is that the central machine
develops a much more complete cache of information that all the clients can take advantage of.
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