Maintained by: NLnet Labs
unbound.conf(5)                  unbound 1.5.1                 unbound.conf(5)



NAME
       unbound.conf - Unbound configuration file.

SYNOPSIS
       unbound.conf

DESCRIPTION
       unbound.conf  is  used  to  configure  unbound(8).  The file format has
       attributes and values. Some attributes  have  attributes  inside  them.
       The notation is: attribute: value.

       Comments  start  with  #  and  last to the end of line. Empty lines are
       ignored as is whitespace at the beginning of a line.

       The utility unbound-checkconf(8) can  be  used  to  check  unbound.conf
       prior to usage.

EXAMPLE
       An    example    config   file   is   shown   below.   Copy   this   to
       /etc/unbound/unbound.conf and start the server with:

            $ unbound -c /etc/unbound/unbound.conf

       Most settings are the defaults. Stop the server with:

            $ kill `cat /etc/unbound/unbound.pid`

       Below is a minimal config file. The  source  distribution  contains  an
       extensive example.conf file with all the options.

       # unbound.conf(5) config file for unbound(8).
       server:
            directory: "/etc/unbound"
            username: unbound
            # make sure unbound can access entropy from inside the chroot.
            # e.g. on linux the use these commands (on BSD, devfs(8) is used):
            #      mount --bind -n /dev/random /etc/unbound/dev/random
            # and  mount --bind -n /dev/log /etc/unbound/dev/log
            chroot: "/etc/unbound"
            # logfile: "/etc/unbound/unbound.log"  #uncomment to use logfile.
            pidfile: "/etc/unbound/unbound.pid"
            # verbosity: 1      # uncomment and increase to get more logging.
            # listen on all interfaces, answer queries from the local subnet.
            interface: 0.0.0.0
            interface: ::0
            access-control: 10.0.0.0/8 allow
            access-control: 2001:DB8::/64 allow

FILE FORMAT
       There  must be whitespace between keywords. Attribute keywords end with
       a colon ':'. An attribute is followed by its containing attributes,  or
       a value.

       Files  can be included using the include: directive. It can appear any-
       where, it accepts a single file name as argument.  Processing continues
       as  if  the text from the included file was copied into the config file
       at that point.  If also using chroot, using full  path  names  for  the
       included files works, relative pathnames for the included names work if
       the directory where the daemon is  started  equals  its  chroot/working
       directory.   Wildcards  can  be  used  to  include  multiple files, see
       glob(7).

   Server Options
       These options are part of the server: clause.

       verbosity: <number>
              The verbosity number, level 0 means no verbosity,  only  errors.
              Level  1  gives  operational information. Level 2 gives detailed
              operational information. Level 3 gives query level  information,
              output  per  query.   Level 4 gives algorithm level information.
              Level 5 logs client identification for cache misses.  Default is
              level  1.  The verbosity can also be increased from the command-
              line, see unbound(8).

       statistics-interval: <seconds>
              The number of seconds between printing statistics to the log for
              every  thread.  Disable with value 0 or "". Default is disabled.
              The histogram statistics are only printed if replies  were  sent
              during  the  statistics  interval,  requestlist  statistics  are
              printed for every interval (but can be 0).  This is because  the
              median calculation requires data to be present.

       statistics-cumulative: <yes or no>
              If  enabled,  statistics  are cumulative since starting unbound,
              without clearing the statistics counters after logging the  sta-
              tistics. Default is no.

       extended-statistics: <yes or no>
              If  enabled,  extended  statistics are printed from unbound-con-
              trol(8).  Default is off, because keeping track of more  statis-
              tics takes time.  The counters are listed in unbound-control(8).

       num-threads: <number>
              The number of threads to create to serve clients. Use 1  for  no
              threading.

       port: <port number>
              The  port  number,  default  53, on which the server responds to
              queries.

       interface: <ip address[@port]>
              Interface to use to connect to the network.  This  interface  is
              listened to for queries from clients, and answers to clients are
              given from it.  Can be given multiple times to work  on  several
              interfaces. If none are given the default is to listen to local-
              host.  The interfaces are not changed on a  reload  (kill  -HUP)
              but  only on restart.  A port number can be specified with @port
              (without spaces between interface and port number), if not spec-
              ified the default port (from port) is used.

       ip-address: <ip address[@port]>
              Same as interface: (for easy of compatibility with nsd.conf).

       interface-automatic: <yes or no>
              Detect source interface on UDP queries and copy them to replies.
              This feature is experimental, and needs support in your  OS  for
              particular socket options.  Default value is no.

       outgoing-interface: <ip address>
              Interface  to  use  to connect to the network. This interface is
              used to send queries to authoritative servers and receive  their
              replies.  Can  be given multiple times to work on several inter-
              faces. If none are given the default  (all)  is  used.  You  can
              specify  the  same  interfaces in interface: and outgoing-inter-
              face: lines, the interfaces are then  used  for  both  purposes.
              Outgoing  queries  are  sent  via a random outgoing interface to
              counter spoofing.

       outgoing-range: <number>
              Number of ports to open. This number of file descriptors can  be
              opened  per  thread. Must be at least 1. Default depends on com-
              pile options. Larger numbers need extra resources from the oper-
              ating system.  For performance a a very large value is best, use
              libevent to make this possible.

       outgoing-port-permit: <port number or range>
              Permit unbound to open this port or range of ports  for  use  to
              send  queries.   A  larger  number  of  permitted outgoing ports
              increases resilience against spoofing attempts. Make sure  these
              ports  are  not  needed by other daemons.  By default only ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

              The  outgoing-port-permit and outgoing-port-avoid statements are
              processed in the line order of the config file, adding the  per-
              mitted  ports  and subtracting the avoided ports from the set of
              allowed ports.  The processing starts with the  non  IANA  allo-
              cated ports above 1024 in the set of allowed ports.

       outgoing-port-avoid: <port number or range>
              Do  not  permit  unbound to open this port or range of ports for
              use to send queries. Use this to make sure unbound does not grab
              a  port  that  another  daemon needs. The port is avoided on all
              outgoing interfaces, both IP4 and IP6.  By  default  only  ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

       outgoing-num-tcp: <number>
              Number  of  outgoing TCP buffers to allocate per thread. Default
              is 10. If set to 0, or if do-tcp is  "no",  no  TCP  queries  to
              authoritative servers are done.

       incoming-num-tcp: <number>
              Number  of  incoming TCP buffers to allocate per thread. Default
              is 10. If set to 0, or if do-tcp is "no", no  TCP  queries  from
              clients are accepted.

       edns-buffer-size: <number>
              Number of bytes size to advertise as the EDNS reassembly  buffer
              size.   This  is  the  value put into datagrams over UDP towards
              peers.  The actual buffer size is determined by  msg-buffer-size
              (both  for  TCP  and  UDP).   Do not set higher than that value.
              Default is 4096 which is RFC recommended.  If you have  fragmen-
              tation  reassembly  problems,  usually  seen as timeouts, then a
              value of 1480 can fix it.  Setting to 512 bypasses even the most
              stringent  path  MTU problems, but is seen as extreme, since the
              amount of TCP fallback generated is excessive (probably also for
              this resolver, consider tuning the outgoing tcp number).

       max-udp-size: <number>
              Maximum  UDP response size (not applied to TCP response).  65536
              disables the udp response size maximum, and uses the choice from
              the  client,  always.  Suggested values are 512 to 4096. Default
              is 4096.

       msg-buffer-size: <number>
              Number of bytes size of the message buffers.  Default  is  65552
              bytes,  enough  for 64 Kb packets, the maximum DNS message size.
              No message larger than this can be  sent  or  received.  Can  be
              reduced to use less memory, but some requests for DNS data, such
              as for huge resource records, will result in a SERVFAIL reply to
              the client.

       msg-cache-size: <number>
              Number  of  bytes  size  of  the  message  cache.  Default  is 4
              megabytes.  A plain number is in bytes, append 'k', 'm'  or  'g'
              for  kilobytes,  megabytes  or  gigabytes  (1024*1024 bytes in a
              megabyte).

       msg-cache-slabs: <number>
              Number of slabs in the message cache.  Slabs  reduce  lock  con-
              tention  by  threads.   Must  be  set  to  a power of 2. Setting
              (close) to the number of cpus is a reasonable guess.

       num-queries-per-thread: <number>
              The number of queries that every thread will service  simultane-
              ously.   If  more  queries  arrive  that  need servicing, and no
              queries can  be  jostled  out  (see  jostle-timeout),  then  the
              queries  are  dropped.  This forces the client to resend after a
              timeout; allowing the  server  time  to  work  on  the  existing
              queries. Default depends on compile options, 512 or 1024.

       jostle-timeout: <msec>
              Timeout  used when the server is very busy.  Set to a value that
              usually results in one roundtrip to the authority  servers.   If
              too  many queries arrive, then 50% of the queries are allowed to
              run to completion, and the other 50% are replaced with  the  new
              incoming  query  if  they  have  already  spent  more than their
              allowed time.  This protects against denial of service  by  slow
              queries  or  high  query  rates.  Default 200 milliseconds.  The
              effect is that the qps for long-lasting queries is  about  (num-
              queriesperthread  /  2)  /  (average time for such long queries)
              qps.  The qps  for  short  queries  can  be  about  (numqueries-
              perthread  /  2)  /  (jostletimeout  in  whole  seconds) qps per
              thread, about (1024/2)*5 = 2560 qps by default.

       delay-close: <msec>
              Extra  delay  for timeouted UDP ports before they are closed, in
              msec.  Default is 0, and that disables it.  This  prevents  very
              delayed  answer  packets  from  the upstream (recursive) servers
              from bouncing against closed ports and setting off all  sort  of
              close-port  counters,  with eg. 1500 msec.  When timeouts happen
              you need extra sockets, it checks the ID and remote IP of  pack-
              ets,  and  unwanted  packets  are  added  to the unwanted packet
              counter.

       so-rcvbuf: <number>
              If not 0, then set the SO_RCVBUF socket option to get more  buf-
              fer space on UDP port 53 incoming queries.  So that short spikes
              on busy servers do not drop  packets  (see  counter  in  netstat
              -su).   Default  is 0 (use system value).  Otherwise, the number
              of bytes to ask for, try "4m" on a busy server.  The OS caps  it
              at  a  maximum, on linux unbound needs root permission to bypass
              the limit, or the admin can use  sysctl  net.core.rmem_max.   On
              BSD  change kern.ipc.maxsockbuf in /etc/sysctl.conf.  On OpenBSD
              change header and recompile kernel. On Solaris ndd -set /dev/udp
              udp_max_buf 8388608.

       so-sndbuf: <number>
              If  not 0, then set the SO_SNDBUF socket option to get more buf-
              fer space on UDP port 53 outgoing queries.  This for  very  busy
              servers  handles  spikes  in  answer  traffic,  otherwise 'send:
              resource temporarily unavailable' can  get  logged,  the  buffer
              overrun  is also visible by netstat -su.  Default is 0 (use sys-
              tem value).  Specify the number of bytes to ask for, try "4m" on
              a  very  busy  server.   The  OS  caps it at a maximum, on linux
              unbound needs root permission to bypass the limit, or the  admin
              can  use  sysctl net.core.wmem_max.  On BSD, Solaris changes are
              similar to so-rcvbuf.

       so-reuseport: <yes or no>
              If yes, then  open  dedicated  listening  sockets  for  incoming
              queries  for  each thread and try to set the SO_REUSEPORT socket
              option on each  socket.   May  distribute  incoming  queries  to
              threads  more  evenly.  Default is no.  On Linux it is supported
              in kernels >= 3.9.  On other systems, FreeBSD, OSX it  may  also
              work.   You  can enable it (on any platform and kernel), it then
              attempts to open the port and passes the option if it was avail-
              able  at compile time, if that works it is used, if it fails, it
              continues silently (unless verbosity 3) without the option.

       rrset-cache-size: <number>
              Number of bytes size of the RRset cache. Default is 4 megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       rrset-cache-slabs: <number>
              Number of slabs in the RRset cache. Slabs reduce lock contention
              by threads.  Must be set to a power of 2.

       cache-max-ttl: <seconds>
              Time  to  live  maximum  for  RRsets  and messages in the cache.
              Default is 86400 seconds (1  day).  If  the  maximum  kicks  in,
              responses  to  clients  still get decrementing TTLs based on the
              original (larger) values.  When the internal  TTL  expires,  the
              cache  item has expired.  Can be set lower to force the resolver
              to query for data often, and not trust (very large) TTL values.

       cache-min-ttl: <seconds>
              Time to live minimum for  RRsets  and  messages  in  the  cache.
              Default  is  0.  If the the minimum kicks in, the data is cached
              for longer than the domain owner intended, and thus less queries
              are  made  to look up the data.  Zero makes sure the data in the
              cache is as the domain owner intended, higher values, especially
              more  than an hour or so, can lead to trouble as the data in the
              cache does not match up with the actual data any more.

       infra-host-ttl: <seconds>
              Time to live for entries in the host cache. The host cache  con-
              tains  roundtrip  timing, lameness and EDNS support information.
              Default is 900.

       infra-cache-slabs: <number>
              Number of slabs in the infrastructure cache. Slabs  reduce  lock
              contention by threads. Must be set to a power of 2.

       infra-cache-numhosts: <number>
              Number  of  hosts  for  which  information is cached. Default is
              10000.

       do-ip4: <yes or no>
              Enable or disable whether ip4 queries are  answered  or  issued.
              Default is yes.

       do-ip6: <yes or no>
              Enable  or  disable  whether ip6 queries are answered or issued.
              Default is yes.  If disabled, queries are not answered on  IPv6,
              and  queries  are  not sent on IPv6 to the internet nameservers.
              With this option you can disable the ipv6 transport for  sending
              DNS traffic, it does not impact the contents of the DNS traffic,
              which may have ip4 and ip6 addresses in it.

       do-udp: <yes or no>
              Enable or disable whether UDP queries are  answered  or  issued.
              Default is yes.

       do-tcp: <yes or no>
              Enable  or  disable  whether TCP queries are answered or issued.
              Default is yes.

       tcp-upstream: <yes or no>
              Enable or disable whether the upstream queries use TCP only  for
              transport.  Default is no.  Useful in tunneling scenarios.

       ssl-upstream: <yes or no>
              Enabled or disable whether the upstream queries use SSL only for
              transport.  Default is no.  Useful in tunneling scenarios.   The
              SSL contains plain DNS in TCP wireformat.  The other server must
              support this (see ssl-service-key).

       ssl-service-key: <file>
              If enabled, the server provider SSL service on its TCP  sockets.
              The clients have to use ssl-upstream: yes.  The file is the pri-
              vate key for the TLS session.  The public certificate is in  the
              ssl-service-pem  file.   Default  is "", turned off.  Requires a
              restart (a reload is not enough) if changed, because the private
              key  is  read  while root permissions are held and before chroot
              (if any).  Normal DNS TCP service  is  not  provided  and  gives
              errors,  this  service is best run with a different port: config
              or @port suffixes in the interface config.

       ssl-service-pem: <file>
              The public  key  certificate  pem  file  for  the  ssl  service.
              Default is "", turned off.

       ssl-port: <number>
              The  port  number  on  which to provide TCP SSL service, default
              443, only interfaces configured with that port number as @number
              get the SSL service.

       do-daemonize: <yes or no>
              Enable  or  disable  whether  the  unbound server forks into the
              background as a daemon. Default is yes.

       access-control: <IP netblock> <action>
              The netblock is given as  an  IP4  or  IP6  address  with  /size
              appended  for a classless network block. The action can be deny,
              refuse, allow, allow_snoop, deny_non_local or refuse_non_local.

              The action deny stops queries from hosts from that netblock.

              The action refuse stops queries  too,  but  sends  a  DNS  rcode
              REFUSED error message back.

              The action allow gives access to clients from that netblock.  It
              gives only access for recursion clients (which  is  what  almost
              all clients need).  Nonrecursive queries are refused.

              The  allow  action does allow nonrecursive queries to access the
              local-data that is configured.  The reason is that this does not
              involve  the  unbound  server  recursive  lookup  algorithm, and
              static data is served in the reply.  This supports normal opera-
              tions  where nonrecursive queries are made for the authoritative
              data.  For nonrecursive queries any  replies  from  the  dynamic
              cache are refused.

              The action allow_snoop gives nonrecursive access too.  This give
              both recursive and non recursive access.  The  name  allow_snoop
              refers  to  cache  snooping,  a  technique  to  use nonrecursive
              queries to examine the  cache  contents  (for  malicious  acts).
              However,  nonrecursive  queries can also be a valuable debugging
              tool (when you want to examine the cache contents). In that case
              use allow_snoop for your administration host.

              By  default only localhost is allowed, the rest is refused.  The
              default is refused, because that is protocol-friendly.  The  DNS
              protocol  is  not designed to handle dropped packets due to pol-
              icy, and dropping may result  in  (possibly  excessive)  retried
              queries.

              The  deny_non_local  and refuse_non_local settings are for hosts
              that are only allowed to query for the authoritative local-data,
              they  are  not  allowed full recursion but only the static data.
              With deny_non_local, messages that are disallowed  are  dropped,
              with refuse_non_local they receive error code REFUSED.

       chroot: <directory>
              If  chroot  is enabled, you should pass the configfile (from the
              commandline) as a full path from the original  root.  After  the
              chroot  has been performed the now defunct portion of the config
              file path is removed to be able to reread  the  config  after  a
              reload.

              All  other  file paths (working dir, logfile, roothints, and key
              files) can be specified in several ways:  as  an  absolute  path
              relative  to  the  new  root,  as a relative path to the working
              directory, or as an absolute path relative to the original root.
              In  the last case the path is adjusted to remove the unused por-
              tion.

              The pidfile can be either a relative path to the working  direc-
              tory,  or  an absolute path relative to the original root. It is
              written just prior to  chroot  and  dropping  permissions.  This
              allows  the pidfile to be /var/run/unbound.pid and the chroot to
              be /var/unbound, for example.

              Additionally,  unbound  may  need  to  access  /dev/random  (for
              entropy) from inside the chroot.

              If given a chroot is done to the given directory. The default is
              "/usr/local/etc/unbound". If you give "" no chroot is performed.

       username: <name>
              If  given,  after  binding  the  port  the  user  privileges are
              dropped. Default is "unbound". If you give username: "" no  user
              change is performed.

              If  this  user  is  not capable of binding the port, reloads (by
              signal HUP) will still retain the opened ports.  If  you  change
              the  port  number  in  the config file, and that new port number
              requires privileges, then a  reload  will  fail;  a  restart  is
              needed.

       directory: <directory>
              Sets   the   working  directory  for  the  program.  Default  is
              "/usr/local/etc/unbound".

       logfile: <filename>
              If "" is given, logging goes to stderr, or nowhere  once  daemo-
              nized.  The logfile is appended to, in the following format:
              [seconds since 1970] unbound[pid:tid]: type: message.
              If  this  option  is  given,  the use-syslog is option is set to
              "no".  The logfile is reopened (for append) when the config file
              is reread, on SIGHUP.

       use-syslog: <yes or no>
              Sets  unbound  to  send  log messages to the syslogd, using sys-
              log(3).  The log facility  LOG_DAEMON  is  used,  with  identity
              "unbound".  The logfile setting is overridden when use-syslog is
              turned on.  The default is to log to syslog.

       log-time-ascii: <yes or no>
              Sets logfile lines to use a timestamp in UTC ascii.  Default  is
              no,  which  prints the seconds since 1970 in brackets. No effect
              if using syslog, in  that  case  syslog  formats  the  timestamp
              printed into the log files.

       log-queries: <yes or no>
              Prints one line per query to the log, with the log timestamp and
              IP address, name, type and class.  Default is no.  Note that  it
              takes time to print these lines which makes the server (signifi-
              cantly) slower.  Odd  (nonprintable)  characters  in  names  are
              printed as '?'.

       pidfile: <filename>
              The   process   id   is   written   to   the  file.  Default  is
              "/usr/local/etc/unbound/unbound.pid".  So,
              kill -HUP `cat /usr/local/etc/unbound/unbound.pid`
              triggers a reload,
              kill -QUIT `cat /usr/local/etc/unbound/unbound.pid`
              gracefully terminates.

       root-hints: <filename>
              Read the root hints from this file. Default  is  nothing,  using
              builtin  hints for the IN class. The file has the format of zone
              files, with  root  nameserver  names  and  addresses  only.  The
              default  may  become outdated, when servers change, therefore it
              is good practice to use a root-hints file.

       hide-identity: <yes or no>
              If enabled id.server and hostname.bind queries are refused.

       identity: <string>
              Set the identity to report. If set to "", the default, then  the
              hostname of the server is returned.

       hide-version: <yes or no>
              If  enabled version.server and version.bind queries are refused.

       version: <string>
              Set the version to report. If set to "", the default,  then  the
              package version is returned.

       target-fetch-policy: <"list of numbers">
              Set  the  target fetch policy used by unbound to determine if it
              should fetch nameserver target addresses opportunistically.  The
              policy is described per dependency depth.

              The  number  of  values  determines the maximum dependency depth
              that unbound will pursue in answering a query.  A  value  of  -1
              means to fetch all targets opportunistically for that dependency
              depth. A value of 0 means to fetch on demand  only.  A  positive
              value fetches that many targets opportunistically.

              Enclose the list between quotes ("") and put spaces between num-
              bers.  The default is "3 2 1 0 0". Setting all zeroes, "0 0 0  0
              0"  gives  behaviour closer to that of BIND 9, while setting "-1
              -1 -1 -1 -1" gives behaviour rumoured to be closer  to  that  of
              BIND 8.

       harden-short-bufsize: <yes or no>
              Very  small  EDNS buffer sizes from queries are ignored. Default
              is off, since it is legal  protocol  wise  to  send  these,  and
              unbound tries to give very small answers to these queries, where
              possible.

       harden-large-queries: <yes or no>
              Very large queries are ignored. Default  is  off,  since  it  is
              legal  protocol  wise  to send these, and could be necessary for
              operation if TSIG or EDNS payload is very large.

       harden-glue: <yes or no>
              Will trust glue only if it  is  within  the  servers  authority.
              Default is on.

       harden-dnssec-stripped: <yes or no>
              Require  DNSSEC  data  for trust-anchored zones, if such data is
              absent, the zone becomes bogus. If turned  off,  and  no  DNSSEC
              data  is  received  (or the DNSKEY data fails to validate), then
              the zone is made insecure, this behaves like there is  no  trust
              anchor.  You  could turn this off if you are sometimes behind an
              intrusive firewall (of some sort) that removes DNSSEC data  from
              packets,  or  a  zone  changes  from signed to unsigned to badly
              signed often. If turned off you run  the  risk  of  a  downgrade
              attack that disables security for a zone. Default is on.

       harden-below-nxdomain: <yes or no>
              From  draft-vixie-dnsext-resimprove, returns nxdomain to queries
              for a name below another name that is already known to be  nxdo-
              main.   DNSSEC  mandates  noerror  for empty nonterminals, hence
              this is possible.  Very old software might return  nxdomain  for
              empty  nonterminals  (that usually happen for reverse IP address
              lookups), and thus may be incompatible with  this.   To  try  to
              avoid  this  only  DNSSEC-secure nxdomains are used, because the
              old software does not have DNSSEC.  Default is off.

       harden-referral-path: <yes or no>
              Harden the referral path by performing  additional  queries  for
              infrastructure data.  Validates the replies if trust anchors are
              configured and the zones are signed.  This enforces DNSSEC vali-
              dation  on  nameserver NS sets and the nameserver addresses that
              are encountered on the referral path  to  the  answer.   Default
              off, because it burdens the authority servers, and it is not RFC
              standard, and could lead to performance problems because of  the
              extra  query  load  that is generated.  Experimental option.  If
              you enable it  consider  adding  more  numbers  after  the  tar-
              get-fetch-policy to increase the max depth that is checked to.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the  query  to  foil  spoof
              attempts.  This perturbs the lowercase and  uppercase  of  query
              names  sent  to  authority servers and checks if the reply still
              has the correct casing.  Disabled by default.  This  feature  is
              an experimental implementation of draft dns-0x20.

       private-address: <IP address or subnet>
              Give  IPv4  of  IPv6  addresses  or classless subnets. These are
              addresses on your private network, and are  not  allowed  to  be
              returned  for  public  internet  names.   Any  occurence of such
              addresses are removed from DNS answers. Additionally, the DNSSEC
              validator  may  mark  the  answers  bogus. This protects against
              so-called DNS Rebinding, where a user browser is turned  into  a
              network  proxy,  allowing  remote  access through the browser to
              other parts of your private network.  Some names can be  allowed
              to contain your private addresses, by default all the local-data
              that you configured is allowed to, and  you  can  specify  addi-
              tional  names  using  private-domain.   No private addresses are
              enabled by default.  We consider to enable this for the  RFC1918
              private  IP  address  space  by  default in later releases. That
              would enable  private  addresses  for  10.0.0.0/8  172.16.0.0/12
              192.168.0.0/16  169.254.0.0/16 fd00::/8 and fe80::/10, since the
              RFC standards say these addresses should not be visible  on  the
              public internet.  Turning on 127.0.0.0/8 would hinder many spam-
              blocklists as they use that.

       private-domain: <domain name>
              Allow this domain, and all its  subdomains  to  contain  private
              addresses.   Give  multiple times to allow multiple domain names
              to contain private addresses. Default is none.

       unwanted-reply-threshold: <number>
              If set, a total number of unwanted replies is kept track  of  in
              every thread.  When it reaches the threshold, a defensive action
              is taken and a warning is printed to  the  log.   The  defensive
              action  is  to  clear  the  rrset  and message caches, hopefully
              flushing away any poison.  A value of 10 million  is  suggested.
              Default is 0 (turned off).

       do-not-query-address: <IP address>
              Do  not  query  the  given IP address. Can be IP4 or IP6. Append
              /num to indicate a classless delegation  netblock,  for  example
              like 10.2.3.4/24 or 2001::11/64.

       do-not-query-localhost: <yes or no>
              If  yes, localhost is added to the do-not-query-address entries,
              both IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost  can  be
              used to send queries to. Default is yes.

       prefetch: <yes or no>
              If yes, message cache elements are prefetched before they expire
              to keep the cache up to date.  Default is  no.   Turning  it  on
              gives about 10 percent more traffic and load on the machine, but
              popular items do not expire from the cache.

       prefetch-key: <yes or no>
              If yes, fetch the DNSKEYs earlier  in  the  validation  process,
              when  a  DS  record  is encountered.  This lowers the latency of
              requests.  It does use a little more CPU.  Also if the cache  is
              set to 0, it is no use. Default is no.

       rrset-roundrobin: <yes or no>
              If yes, Unbound rotates RRSet order in response (the random num-
              ber is taken from the query ID, for speed  and  thread  safety).
              Default is no.

       minimal-responses: <yes or no>
              If  yes,  Unbound  doesn't  insert authority/additional sections
              into response messages when those  sections  are  not  required.
              This  reduces  response  size  significantly,  and may avoid TCP
              fallback for some responses.  This may cause a  slight  speedup.
              The  default  is no, because the DNS protocol RFCs mandate these
              sections, and the additional content could be of  use  and  save
              roundtrips for clients.

       module-config: <"module names">
              Module  configuration,  a list of module names separated by spa-
              ces, surround the string with quotes (""). The  modules  can  be
              validator,  iterator.  Setting this to "iterator" will result in
              a non-validating server.  Setting this to  "validator  iterator"
              will  turn on DNSSEC validation.  The ordering of the modules is
              important.  You must also set trust-anchors for validation to be
              useful.

       trust-anchor-file: <filename>
              File  with  trusted  keys  for  validation.  Both  DS and DNSKEY
              entries can appear in the file. The format of the  file  is  the
              standard  DNS  Zone  file  format.   Default  is "", or no trust
              anchor file.

       auto-trust-anchor-file: <filename>
              File with trust anchor for  one  zone,  which  is  tracked  with
              RFC5011  probes.   The  probes are several times per month, thus
              the machine must be online frequently.  The initial file can  be
              one  with  contents as described in trust-anchor-file.  The file
              is written to when the anchor is updated, so  the  unbound  user
              must have write permission.

       trust-anchor: <"Resource Record">
              A  DS  or  DNSKEY  RR  for a key to use for validation. Multiple
              entries can be given to specify multiple trusted keys, in  addi-
              tion  to the trust-anchor-files.  The resource record is entered
              in the same format as 'dig' or 'drill'  prints  them,  the  same
              format  as in the zone file. Has to be on a single line, with ""
              around it. A TTL can be specified for ease of cut and paste, but
              is  ignored.  A class can be specified, but class IN is default.

       trusted-keys-file: <filename>
              File with trusted keys for validation.  Specify  more  than  one
              file   with   several   entries,   one   file  per  entry.  Like
              trust-anchor-file but has a different  file  format.  Format  is
              BIND-9  style  format,  the  trusted-keys { name flag proto algo
              "key"; }; clauses are read.  It is  possible  to  use  wildcards
              with  this  statement,  the wildcard is expanded on start and on
              reload.

       dlv-anchor-file: <filename>
              File with trusted keys for DLV  (DNSSEC  Lookaside  Validation).
              Both  DS and DNSKEY entries can be used in the file, in the same
              format as for trust-anchor-file: statements. Only one DLV can be
              configured,  more would be slow. The DLV configured is used as a
              root trusted DLV, this means that it  is  a  lookaside  for  the
              root. Default is "", or no dlv anchor file.

       dlv-anchor: <"Resource Record">
              Much  like  trust-anchor,  this  is  a DLV anchor with the DS or
              DNSKEY inline.

       domain-insecure: <domain name>
              Sets domain name to  be  insecure,  DNSSEC  chain  of  trust  is
              ignored  towards  the  domain name.  So a trust anchor above the
              domain name can not make the domain secure  with  a  DS  record,
              such  a  DS  record  is  then  ignored.   Also keys from DLV are
              ignored for the domain.  Can be given multiple times to  specify
              multiple  domains  that  are treated as if unsigned.  If you set
              trust anchors for the domain they override this setting (and the
              domain is secured).

              This  can  be useful if you want to make sure a trust anchor for
              external lookups does not affect an (unsigned) internal  domain.
              A  DS  record externally can create validation failures for that
              internal domain.

       val-override-date: <rrsig-style date spec>
              Default is "" or "0", which disables this debugging feature.  If
              enabled by giving a RRSIG style date, that date is used for ver-
              ifying RRSIG inception and expiration dates, instead of the cur-
              rent  date.  Do  not set this unless you are debugging signature
              inception and expiration. The value -1 ignores  the  date  alto-
              gether, useful for some special applications.

       val-sig-skew-min: <seconds>
              Minimum  number  of  seconds of clock skew to apply to validated
              signatures.  A value of 10% of the signature  lifetime  (expira-
              tion  -  inception) is used, capped by this setting.  Default is
              3600 (1 hour) which allows  for  daylight  savings  differences.
              Lower  this value for more strict checking of short lived signa-
              tures.

       val-sig-skew-max: <seconds>
              Maximum number of seconds of clock skew to  apply  to  validated
              signatures.   A  value of 10% of the signature lifetime (expira-
              tion - inception) is used, capped by this setting.   Default  is
              86400  (24  hours) which allows for timezone setting problems in
              stable domains.  Setting both min and max very low disables  the
              clock skew allowances.  Setting both min and max very high makes
              the validator check the signature timestamps less strictly.

       val-bogus-ttl: <number>
              The time to live for bogus data. This is data  that  has  failed
              validation;  due  to invalid signatures or other checks. The TTL
              from that data  cannot  be  trusted,  and  this  value  is  used
              instead. The value is in seconds, default 60.  The time interval
              prevents repeated revalidation of bogus data.

       val-clean-additional: <yes or no>
              Instruct the validator to remove data from the  additional  sec-
              tion  of  secure messages that are not signed properly. Messages
              that are insecure, bogus, indeterminate  or  unchecked  are  not
              affected.  Default is yes. Use this setting to protect the users
              that rely on this validator for authentication from protentially
              bad data in the additional section.

       val-log-level: <number>
              Have  the  validator  print  validation  failures  to  the  log.
              Regardless of the verbosity setting.  Default is 0, off.  At  1,
              for  every  user query that fails a line is printed to the logs.
              This way you can monitor what happens with  validation.   Use  a
              diagnosis tool, such as dig or drill, to find out why validation
              is failing for these queries.  At 2, not  only  the  query  that
              failed is printed but also the reason why unbound thought it was
              wrong and which server sent the faulty data.

       val-permissive-mode: <yes or no>
              Instruct the validator to mark bogus messages as  indeterminate.
              The  security  checks  are performed, but if the result is bogus
              (failed security), the reply is not  withheld  from  the  client
              with  SERVFAIL as usual. The client receives the bogus data. For
              messages that are found to be  secure  the  AD  bit  is  set  in
              replies.  Also logging is performed as for full validation.  The
              default value is "no".

       ignore-cd-flag: <yes or no>
              Instruct unbound to ignore the CD flag from clients  and  refuse
              to  return  bogus  answers to them.  Thus, the CD (Checking Dis-
              abled) flag does not disable checking any more.  This is  useful
              if  legacy (w2008) servers that set the CD flag but cannot vali-
              date DNSSEC themselves are the clients, and  then  unbound  pro-
              vides them with DNSSEC protection.  The default value is "no".

       val-nsec3-keysize-iterations: <"list of values">
              List of keysize and iteration count values, separated by spaces,
              surrounded by quotes. Default is "1024 150 2048 500 4096  2500".
              This determines the maximum allowed NSEC3 iteration count before
              a message is simply marked insecure instead  of  performing  the
              many hashing iterations. The list must be in ascending order and
              have at least one entry. If you set it to "1024 65535" there  is
              no  restriction  to  NSEC3 iteration values.  This table must be
              kept short; a very long list could cause slower operation.

       add-holddown: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates to add new trust anchors only after they have
              been visible for this time.  Default is 30 days as per the  RFC.

       del-holddown: <seconds>
              Instruct  the auto-trust-anchor-file probe mechanism for RFC5011
              autotrust updates to remove revoked  trust  anchors  after  they
              have been kept in the revoked list for this long.  Default is 30
              days as per the RFC.

       keep-missing: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates  to  remove  missing trust anchors after they
              have been unseen for this long.  This cleans up the  state  file
              if  the target zone does not perform trust anchor revocation, so
              this makes the auto probe mechanism work with zones that perform
              regular  (non-5011)  rollovers.   The  default is 366 days.  The
              value 0 does not remove missing anchors, as per the RFC.

       key-cache-size: <number>
              Number of bytes size of the key cache. Default is  4  megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       key-cache-slabs: <number>
              Number of slabs in the key cache. Slabs reduce  lock  contention
              by threads.  Must be set to a power of 2. Setting (close) to the
              number of cpus is a reasonable guess.

       neg-cache-size: <number>
              Number of bytes size of the aggressive negative  cache.  Default
              is  1  megabyte.  A plain number is in bytes, append 'k', 'm' or
              'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in  a
              megabyte).

       unblock-lan-zones: <yesno>
              Default  is  disabled.   If  enabled,  then  for private address
              space, the reverse lookups are no longer filtered.  This  allows
              unbound  when running as dns service on a host where it provides
              service for that host, to put out all of  the  queries  for  the
              'lan' upstream.  When enabled, only localhost, 127.0.0.1 reverse
              and ::1 reverse zones are configured with default  local  zones.
              Disable the option when unbound is running as a (DHCP-) DNS net-
              work resolver for a group of machines, where such lookups should
              be  filtered  (RFC  compliance),  this also stops potential data
              leakage about the local network to the upstream DNS servers.

       local-zone: <zone> <type>
              Configure a local zone. The type determines the answer  to  give
              if  there  is  no  match  from  local-data.  The types are deny,
              refuse, static, transparent, redirect, nodefault,  typetranspar-
              ent,  and  are  explained below. After that the default settings
              are listed. Use local-data: to enter data into the  local  zone.
              Answers  for  local  zones  are  authoritative  DNS  answers. By
              default the zones are class IN.

              If you need more complicated authoritative data, with referrals,
              wildcards, CNAME/DNAME support, or DNSSEC authoritative service,
              setup a stub-zone for it as detailed in the  stub  zone  section
              below.

            deny Do  not  send an answer, drop the query.  If there is a match
                 from local data, the query is answered.

            refuse
                 Send an error message reply, with rcode REFUSED.  If there is
                 a match from local data, the query is answered.

            static
                 If  there  is a match from local data, the query is answered.
                 Otherwise, the query is answered  with  nodata  or  nxdomain.
                 For  a  negative  answer  a  SOA is included in the answer if
                 present as local-data for the zone apex domain.

            transparent
                 If there is a match from local data, the query  is  answered.
                 Otherwise  if  the  query  has a different name, the query is
                 resolved normally.  If the query  is  for  a  name  given  in
                 localdata  but  no  such  type of data is given in localdata,
                 then a noerror nodata answer is returned.  If  no  local-zone
                 is  given  local-data causes a transparent zone to be created
                 by default.

            typetransparent
                 If there is a match from local data, the query  is  answered.
                 If  the  query  is for a different name, or for the same name
                 but for a different type, the  query  is  resolved  normally.
                 So,  similar  to transparent but types that are not listed in
                 local data are resolved normally, so if an A record is in the
                 local  data  that  does  not  cause  a  nodata reply for AAAA
                 queries.

            redirect
                 The query is answered from the local data for the zone  name.
                 There  may  be  no  local  data  beneath the zone name.  This
                 answers queries for the zone, and all subdomains of the  zone
                 with the local data for the zone.  It can be used to redirect
                 a domain to return a different  address  record  to  the  end
                 user,    with   local-zone:   "example.com."   redirect   and
                 local-data: "example.com. A 127.0.0.1" queries for  www.exam-
                 ple.com and www.foo.example.com are redirected, so that users
                 with web browsers  cannot  access  sites  with  suffix  exam-
                 ple.com.

            nodefault
                 Used  to turn off default contents for AS112 zones. The other
                 types also turn off default contents for the zone. The 'node-
                 fault'  option  has  no other effect than turning off default
                 contents for the given zone.

       The default zones are localhost, reverse 127.0.0.1  and  ::1,  and  the
       AS112  zones. The AS112 zones are reverse DNS zones for private use and
       reserved IP addresses for which the servers on the internet cannot pro-
       vide  correct  answers. They are configured by default to give nxdomain
       (no reverse information) answers. The defaults can  be  turned  off  by
       specifying  your  own local-zone of that name, or using the 'nodefault'
       type. Below is a list of the default zone contents.

            localhost
                 The IP4 and IP6 localhost information is given.  NS  and  SOA
                 records are provided for completeness and to satisfy some DNS
                 update tools. Default content:
                 local-zone: "localhost." static
                 local-data: "localhost. 10800 IN NS localhost."
                 local-data: "localhost. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "localhost. 10800 IN A 127.0.0.1"
                 local-data: "localhost. 10800 IN AAAA ::1"

            reverse IPv4 loopback
                 Default content:
                 local-zone: "127.in-addr.arpa." static
                 local-data: "127.in-addr.arpa. 10800 IN NS localhost."
                 local-data: "127.in-addr.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.127.in-addr.arpa. 10800 IN
                     PTR localhost."

            reverse IPv6 loopback
                 Default content:
                 local-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     NS localhost."
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     PTR localhost."

            reverse RFC1918 local use zones
                 Reverse data for zones  10.in-addr.arpa,  16.172.in-addr.arpa
                 to     31.172.in-addr.arpa,     168.192.in-addr.arpa.     The
                 local-zone: is set static  and  as  local-data:  SOA  and  NS
                 records are provided.

            reverse RFC3330 IP4 this, link-local, testnet and broadcast
                 Reverse  data for zones 0.in-addr.arpa, 254.169.in-addr.arpa,
                 2.0.192.in-addr.arpa (TEST  NET  1),  100.51.198.in-addr.arpa
                 (TEST   NET   2),   113.0.203.in-addr.arpa   (TEST   NET  3),
                 255.255.255.255.in-addr.arpa.  And  from  64.100.in-addr.arpa
                 to 127.100.in-addr.arpa (Shared Address Space).

            reverse RFC4291 IP6 unspecified
                 Reverse data for zone
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.

            reverse RFC4193 IPv6 Locally Assigned Local Addresses
                 Reverse data for zone D.F.ip6.arpa.

            reverse RFC4291 IPv6 Link Local Addresses
                 Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.

            reverse IPv6 Example Prefix
                 Reverse  data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is
                 used for tutorials and examples. You can remove the block  on
                 this zone with:
                   local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
                 You can also selectively unblock a part of the zone by making
                 that part transparent with a local-zone statement.  This also
                 works with the other default zones.

       local-data: "<resource record string>"
            Configure  local data, which is served in reply to queries for it.
            The query has to match exactly unless you configure the local-zone
            as  redirect.  If  not matched exactly, the local-zone type deter-
            mines further processing. If local-data is configured that is  not
            a  subdomain  of a local-zone, a transparent local-zone is config-
            ured.  For record types such as TXT,  use  single  quotes,  as  in
            local-data: 'example. TXT "text"'.

            If  you  need more complicated authoritative data, with referrals,
            wildcards, CNAME/DNAME support, or DNSSEC  authoritative  service,
            setup  a  stub-zone  for  it  as detailed in the stub zone section
            below.

       local-data-ptr: "IPaddr name"
            Configure local data shorthand for a PTR record with the  reversed
            IPv4  or  IPv6  address and the host name.  For example "192.0.2.4
            www.example.com".  TTL can be  inserted  like  this:  "2001:DB8::4
            7200 www.example.com"

   Remote Control Options
       In  the remote-control: clause are the declarations for the remote con-
       trol facility.  If this is enabled, the unbound-control(8) utility  can
       be  used  to  send  commands to the running unbound server.  The server
       uses these clauses to setup SSLv3 / TLSv1 security for the  connection.
       The  unbound-control(8)  utility  also reads the remote-control section
       for options.  To setup the correct  self-signed  certificates  use  the
       unbound-control-setup(8) utility.

       control-enable: <yes or no>
            The  option is used to enable remote control, default is "no".  If
            turned off, the server does not listen for control commands.

       control-interface: <ip address>
            Give IPv4 or IPv6 addresses to listen on for control commands.  By
            default localhost (127.0.0.1 and ::1) is listened to.  Use 0.0.0.0
            and ::0 to listen to all interfaces.

       control-port: <port number>
            The port number to listen on  for  control  commands,  default  is
            8953.   If  you change this port number, and permissions have been
            dropped, a reload is not sufficient to open the  port  again,  you
            must then restart.

       server-key-file: <private key file>
            Path  to  the  server  private key, by default unbound_server.key.
            This file is generated by the unbound-control-setup utility.  This
            file is used by the unbound server, but not by unbound-control.

       server-cert-file: <certificate file.pem>
            Path   to   the   server   self  signed  certificate,  by  default
            unbound_server.pem.  This file is generated  by  the  unbound-con-
            trol-setup  utility.  This file is used by the unbound server, and
            also by unbound-control.

       control-key-file: <private key file>
            Path to the control client private key,  by  default  unbound_con-
            trol.key.   This  file  is  generated by the unbound-control-setup
            utility.  This file is used by unbound-control.

       control-cert-file: <certificate file.pem>
            Path to the control client certificate,  by  default  unbound_con-
            trol.pem.   This certificate has to be signed with the server cer-
            tificate.  This file is  generated  by  the  unbound-control-setup
            utility.  This file is used by unbound-control.

   Stub Zone Options
       There may be multiple stub-zone: clauses. Each with a name: and zero or
       more hostnames or IP addresses.  For the stub zone this list  of  name-
       servers  is used. Class IN is assumed.  The servers should be authority
       servers, not  recursors;  unbound  performs  the  recursive  processing
       itself for stub zones.

       The stub zone can be used to configure authoritative data to be used by
       the resolver that cannot be accessed using the public internet servers.
       This  is  useful  for  company-local  data  or  private zones. Setup an
       authoritative server on a different host (or different port).  Enter  a
       config  entry  for unbound with stub-addr: <ip address of host[@port]>.
       The unbound resolver can then access the data, without referring to the
       public internet for it.

       This  setup  allows DNSSEC signed zones to be served by that authorita-
       tive server, in which case a trusted key entry with the public key  can
       be  put in config, so that unbound can validate the data and set the AD
       bit on replies for the private zone (authoritative servers do  not  set
       the AD bit).  This setup makes unbound capable of answering queries for
       the private zone, and can even set the AD bit ('authentic'), but the AA
       ('authoritative') bit is not set on these replies.

       name: <domain name>
              Name of the stub zone.

       stub-host: <domain name>
              Name  of  stub  zone nameserver. Is itself resolved before it is
              used.

       stub-addr: <IP address>
              IP address of stub zone nameserver. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.

       stub-prime: <yes or no>
              This option is by default off.  If enabled it  performs  NS  set
              priming,  which  is similar to root hints, where it starts using
              the list of nameservers currently published by the zone.   Thus,
              if  the  hint list is slightly outdated, the resolver picks up a
              correct list online.

       stub-first: <yes or no>
              If enabled, a query is attempted without the stub clause  if  it
              fails.   The  data  could not be retrieved and would have caused
              SERVFAIL because the servers  are  unreachable,  instead  it  is
              tried without this clause.  The default is no.

   Forward Zone Options
       There may be multiple forward-zone: clauses. Each with a name: and zero
       or more hostnames or IP addresses.  For the forward zone this  list  of
       nameservers  is  used  to forward the queries to. The servers listed as
       forward-host: and forward-addr: have to handle  further  recursion  for
       the  query.   Thus,  those  servers  are not authority servers, but are
       (just like unbound is) recursive servers too; unbound does not  perform
       recursion itself for the forward zone, it lets the remote server do it.
       Class IN is assumed.  A forward-zone entry with name  "."  and  a  for-
       ward-addr  target will forward all queries to that other server (unless
       it can answer from the cache).

       name: <domain name>
              Name of the forward zone.

       forward-host: <domain name>
              Name of server to forward to. Is itself resolved  before  it  is
              used.

       forward-addr: <IP address>
              IP address of server to forward to. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.

       forward-first: <yes or no>
              If  enabled,  a query is attempted without the forward clause if
              it fails.  The data could not be retrieved and would have caused
              SERVFAIL  because  the  servers  are  unreachable, instead it is
              tried without this clause.  The default is no.

   Python Module Options
       The python: clause gives the settings for the python(1) script  module.
       This module acts like the iterator and validator modules do, on queries
       and answers.  To enable the script module it has to  be  compiled  into
       the  daemon,  and the word "python" has to be put in the module-config:
       option (usually first, or between the validator and iterator).

       python-script: <python file>
              The script file to load.

   DNS64 Module Options
       The dns64 module must be configured in the module-config:  "dns64  val-
       idator  iterator"  directive  and  be  compiled  into  the daemon to be
       enabled.  These settings go in the server: section.

       dns64-prefix: <IPv6 prefix>
              This sets the DNS64 prefix to use  to  synthesize  AAAA  records
              with.   It  must  be  /96  or  shorter.   The  default prefix is
              64:ff9b::/96.

       dns64-synthall: <yes or no>
              Debug option, default  no.   If  enabled,  synthesize  all  AAAA
              records despite the presence of actual AAAA records.

MEMORY CONTROL EXAMPLE
       In the example config settings below memory usage is reduced. Some ser-
       vice levels are lower, notable very large data and a high TCP load  are
       no longer supported. Very large data and high TCP loads are exceptional
       for the DNS.  DNSSEC validation is enabled, just add trust anchors.  If
       you do not have to worry about programs using more than 3 Mb of memory,
       the below example is not for you. Use the defaults to receive full ser-
       vice, which on BSD-32bit tops out at 30-40 Mb after heavy usage.

       # example settings that reduce memory usage
       server:
            num-threads: 1
            outgoing-num-tcp: 1 # this limits TCP service, uses less buffers.
            incoming-num-tcp: 1
            outgoing-range: 60  # uses less memory, but less performance.
            msg-buffer-size: 8192   # note this limits service, 'no huge stuff'.
            msg-cache-size: 100k
            msg-cache-slabs: 1
            rrset-cache-size: 100k
            rrset-cache-slabs: 1
            infra-cache-numhosts: 200
            infra-cache-slabs: 1
            key-cache-size: 100k
            key-cache-slabs: 1
            neg-cache-size: 10k
            num-queries-per-thread: 30
            target-fetch-policy: "2 1 0 0 0 0"
            harden-large-queries: "yes"
            harden-short-bufsize: "yes"

FILES
       /usr/local/etc/unbound
              default unbound working directory.

       /usr/local/etc/unbound
              default chroot(2) location.

       /usr/local/etc/unbound/unbound.conf
              unbound configuration file.

       /usr/local/etc/unbound/unbound.pid
              default unbound pidfile with process ID of the running daemon.

       unbound.log
              unbound log file. default is to log to syslog(3).

SEE ALSO
       unbound(8), unbound-checkconf(8).

AUTHORS
       Unbound  was written by NLnet Labs. Please see CREDITS file in the dis-
       tribution for further details.



NLnet Labs                       Dec  8, 2014                  unbound.conf(5)