Bv9ARM.ch05.html revision cebe3ec7c5ba5003acc05142d4368af2a3a261e9
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowe>The BIND 9 Lightweight Resolver</TITLE
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweNAME="GENERATOR"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCONTENT="Modular DocBook HTML Stylesheet Version 1.41"><LINK
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweREL="PREVIOUS"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweTITLE="Advanced Concepts"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenTITLE="BIND 9 Configuration Reference"
6a72db4a7fa12c3e0d1c1cf91a07390739fa0fbfBryan CantrillBGCOLOR="#FFFFFF"
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a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovVLINK="#840084"
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ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenCELLPADDING="0"
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ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenVALIGN="bottom"
95c635efb7c3b86efc493e0447eaec7aecca3f0fGarrett D'AmoreALIGN="center"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenVALIGN="bottom"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenVALIGN="bottom"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenCLASS="chapter"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>Chapter 5. The <SPAN
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenCLASS="acronym"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden> 9 Lightweight Resolver</A
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>Table of Contents</B
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>The Lightweight Resolver Library</A
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>Running a Resolver Daemon</A
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>5.1. The Lightweight Resolver Library</A
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>Traditionally applications have been linked with a stub resolver
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidenlibrary that sends recursive DNS queries to a local caching name
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>IPv6 introduces new complexity into the resolution process,
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidensuch as following A6 chains and DNAME records, and simultaneous
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidenlookup of IPv4 and IPv6 addresses. These are hard or impossible
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidento implement in a traditional stub resolver.</P
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>Instead, <SPAN
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenCLASS="acronym"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden> 9 provides resolution services to local clients
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidenusing a combination of a lightweight resolver library and a resolver
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidendaemon process running on the local host. These communicate using
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidena simple UDP-based protocol, the "lightweight resolver protocol"
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidenthat is distinct from and simpler than the full DNS protocol.</P
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>5.2. Running a Resolver Daemon</A
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Siden>To use the lightweight resolver interface, the system must
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher Sidenrun the resolver daemon <B
ad135b5d644628e791c3188a6ecbd9c257961ef8Christopher SidenCLASS="command"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowe>By default, applications using the lightweight resolver library will make
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweUDP requests to the IPv4 loopback address (127.0.0.1) on port 921. The
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Loweaddress can be overriden by <B
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCLASS="command"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCLASS="filename"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweThe daemon will try to find the answer to the questions "what are the
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Loweaddresses for host
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCLASS="literal"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowe>?" and "what are
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowethe names for IPv4 address 10.1.2.3?"</P
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowe>The daemon currently only looks in the DNS, but in the future
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Loweit may use other sources such as <TT
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCLASS="filename"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCLASS="command"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowe> daemon is essentially a
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Lowecaching-only name server that answers requests using the lightweight
c10c16dec587a0662068f6e2991c29ed3a9db943Richard Loweresolver protocol rather than the DNS protocol. Because it needs
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankovto run on each host, it is designed to require no or minimal configuration.
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovUnless configured otherwise, it uses the name servers listed on
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="command"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov>nameserver</B
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov> lines in <TT
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="filename"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankovas forwarders, but is also capable of doing the resolution autonomously if
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankovnone are specified.</P
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="command"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov> daemon may also be configured with a
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="filename"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov> style configuration file, in
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="filename"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov> by default. A name server may also
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankovbe configured to act as a lightweight resolver daemon using the
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="command"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri Pankov> statement in <TT
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="filename"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCLASS="NAVFOOTER"
a9478106a12424322498e53cf7cd75bd8a4d6004Yuri PankovCELLPADDING="0"
c10c16dec587a0662068f6e2991c29ed3a9db943Richard LoweCELLSPACING="0"
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