path: root/external/unbound/doc/unbound.conf.5.in

.TH "unbound.conf" "5" "@date@" "NLnet Labs" "unbound @version@"
.\"
.\" unbound.conf.5 -- unbound.conf manual
.\"
.\" Copyright (c) 2007, NLnet Labs. All rights reserved.
.\"
.\" See LICENSE for the license.
.\"
.\"
.SH "NAME"
.B unbound.conf
\- Unbound configuration file.
.SH "SYNOPSIS"
.B unbound.conf
.SH "DESCRIPTION"
.B unbound.conf
is used to configure
\fIunbound\fR(8).
The file format has attributes and values. Some attributes have attributes inside them.
The notation is: attribute: value.
.P
Comments start with # and last to the end of line. Empty lines are
ignored as is whitespace at the beginning of a line.
.P
The utility 
\fIunbound\-checkconf\fR(8)
can be used to check unbound.conf prior to usage.
.SH "EXAMPLE"
An example config file is shown below. Copy this to /etc/unbound/unbound.conf
and start the server with:
.P
.nf
	$ unbound \-c /etc/unbound/unbound.conf 
.fi
.P
Most settings are the defaults. Stop the server with:
.P
.nf
	$ kill `cat /etc/unbound/unbound.pid`
.fi
.P
Below is a minimal config file. The source distribution contains an extensive
example.conf file with all the options.
.P
.nf
# 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
.fi
.SH "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.
.P
Files can be included using the
.B include:
directive. It can appear anywhere, 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 \fIglob\fR(7).
.SS "Server Options"
These options are part of the
.B server:
clause.
.TP
.B verbosity: \fI<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 commandline, see \fIunbound\fR(8).
.TP
.B statistics\-interval: \fI<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.
.TP
.B statistics\-cumulative: \fI<yes or no>
If enabled, statistics are cumulative since starting unbound, without clearing
the statistics counters after logging the statistics. Default is no.
.TP
.B extended\-statistics: \fI<yes or no>
If enabled, extended statistics are printed from \fIunbound\-control\fR(8). 
Default is off, because keeping track of more statistics takes time.  The
counters are listed in \fIunbound\-control\fR(8).
.TP
.B num\-threads: \fI<number>
The number of threads to create to serve clients. Use 1 for no threading.
.TP
.B port: \fI<port number>
The port number, default 53, on which the server responds to queries.
.TP
.B interface: \fI<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 localhost.
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 specified the default port (from
\fBport\fR) is used.
.TP
.B ip\-address: \fI<ip address[@port]>
Same as interface: (for easy of compatibility with nsd.conf).
.TP
.B interface\-automatic: \fI<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.
.TP
.B outgoing\-interface: \fI<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 interfaces. If none are given the 
default (all) is used. You can specify the same interfaces in 
.B interface:
and
.B outgoing\-interface:
lines, the interfaces are then used for both purposes. Outgoing queries are 
sent via a random outgoing interface to counter spoofing.
.TP
.B outgoing\-range: \fI<number>
Number of ports to open. This number of file descriptors can be opened per 
thread. Must be at least 1. Default depends on compile options. Larger 
numbers need extra resources from the operating system.  For performance a
a very large value is best, use libevent to make this possible.
.TP
.B outgoing\-port\-permit: \fI<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.
.IP
The \fBoutgoing\-port\-permit\fR and \fBoutgoing\-port\-avoid\fR statements 
are processed in the line order of the config file, adding the permitted ports 
and subtracting the avoided ports from the set of allowed ports.  The 
processing starts with the non IANA allocated ports above 1024 in the set 
of allowed ports.
.TP
.B outgoing\-port\-avoid: \fI<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.
.TP
.B outgoing\-num\-tcp: \fI<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.  For larger installations increasing this value is a good idea.
.TP
.B incoming\-num\-tcp: \fI<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. For larger installations increasing this value is a good idea.
.TP
.B edns\-buffer\-size: \fI<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 fragmentation 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).
.TP
.B max\-udp\-size: \fI<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. 
.TP
.B msg\-buffer\-size: \fI<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.
.TP
.B msg\-cache\-size: \fI<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).
.TP
.B msg\-cache\-slabs: \fI<number>
Number of slabs in the message 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.
.TP
.B num\-queries\-per\-thread: \fI<number>
The number of queries that every thread will service simultaneously.
If more queries arrive that need servicing, and no queries can be jostled out
(see \fIjostle\-timeout\fR), 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.
.TP
.B jostle\-timeout: \fI<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 
(numqueriesperthread / 2) / (average time for such long queries) qps.
The qps for short queries can be about (numqueriesperthread / 2)
/ (jostletimeout in whole seconds) qps per thread, about (1024/2)*5 = 2560
qps by default.
.TP
.B delay\-close: \fI<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 packets, and unwanted packets are added to the
unwanted packet counter.
.TP
.B so\-rcvbuf: \fI<number>
If not 0, then set the SO_RCVBUF socket option to get more buffer
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.
.TP
.B so\-sndbuf: \fI<number>
If not 0, then set the SO_SNDBUF socket option to get more buffer 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 system 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.
.TP
.B so\-reuseport: \fI<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 available
at compile time, if that works it is used, if it fails, it continues
silently (unless verbosity 3) without the option.
.TP
.B ip\-transparent: \fI<yes or no>
If yes, then use IP_TRANSPARENT socket option on sockets where unbound
is listening for incoming traffic.  Default no.  Allows you to bind to
non\-local interfaces.  For example for non\-existant IP addresses that
are going to exist later on, with host failover configuration.  This is
a lot like interface\-automatic, but that one services all interfaces
and with this option you can select which (future) interfaces unbound
provides service on.  This option needs unbound to be started with root
permissions on some systems.
.TP
.B rrset\-cache\-size: \fI<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 kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B rrset\-cache\-slabs: \fI<number>
Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
Must be set to a power of 2. 
.TP
.B cache\-max\-ttl: \fI<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.
.TP
.B cache\-min\-ttl: \fI<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.
.TP
.B infra\-host\-ttl: \fI<seconds>
Time to live for entries in the host cache. The host cache contains 
roundtrip timing, lameness and EDNS support information. Default is 900.
.TP
.B infra\-cache\-slabs: \fI<number>
Number of slabs in the infrastructure cache. Slabs reduce lock contention 
by threads. Must be set to a power of 2. 
.TP
.B infra\-cache\-numhosts: \fI<number>
Number of hosts for which information is cached. Default is 10000.
.TP
.B infra\-cache\-min\-rtt: \fI<msec>
Lower limit for dynamic retransmit timeout calculation in infrastructure
cache. Default is 50 milliseconds. Increase this value if using forwarders
needing more time to do recursive name resolution.
.TP
.B do\-ip4: \fI<yes or no>
Enable or disable whether ip4 queries are answered or issued. Default is yes.
.TP
.B do\-ip6: \fI<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.
.TP
.B do\-udp: \fI<yes or no>
Enable or disable whether UDP queries are answered or issued. Default is yes.
.TP
.B do\-tcp: \fI<yes or no>
Enable or disable whether TCP queries are answered or issued. Default is yes.
.TP
.B tcp\-upstream: \fI<yes or no>
Enable or disable whether the upstream queries use TCP only for transport.
Default is no.  Useful in tunneling scenarios.
.TP
.B ssl\-upstream: \fI<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 \fBssl\-service\-key\fR).
.TP
.B ssl\-service-key: \fI<file>
If enabled, the server provider SSL service on its TCP sockets.  The clients
have to use ssl\-upstream: yes.  The file is the private 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 \fBport:\fR config or \fI@port\fR
suffixes in the \fBinterface\fR config.
.TP
.B ssl\-service\-pem: \fI<file>
The public key certificate pem file for the ssl service.  Default is "",
turned off.
.TP
.B ssl\-port: \fI<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.
.TP
.B do\-daemonize: \fI<yes or no>
Enable or disable whether the unbound server forks into the background as
a daemon. Default is yes.
.TP
.B access\-control: \fI<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 \fIdeny\fR, \fIrefuse\fR, 
\fIallow\fR, \fIallow_snoop\fR, \fIdeny_non_local\fR or \fIrefuse_non_local\fR.
.IP
The action \fIdeny\fR stops queries from hosts from that netblock.
.IP
The action \fIrefuse\fR stops queries too, but sends a DNS rcode REFUSED 
error message back.
.IP
The action \fIallow\fR 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.
.IP
The \fIallow\fR 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 operations where nonrecursive queries 
are made for the authoritative data.  For nonrecursive queries any replies 
from the dynamic cache are refused.
.IP
The action \fIallow_snoop\fR gives nonrecursive access too.  This give 
both recursive and non recursive access.  The name \fIallow_snoop\fR 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 \fIallow_snoop\fR for your administration host.
.IP
By default only localhost is \fIallow\fRed, the rest is \fIrefuse\fRd.
The default is \fIrefuse\fRd, because that is protocol\-friendly. The DNS 
protocol is not designed to handle dropped packets due to policy, and 
dropping may result in (possibly excessive) retried queries.
.IP
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.
.TP
.B chroot: \fI<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. 
.IP
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 portion.
.IP
The pidfile can be either a relative path to the working directory, 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.
.IP
Additionally, unbound may need to access /dev/random (for entropy)
from inside the chroot.
.IP
If given a chroot is done to the given directory. The default is 
"@UNBOUND_CHROOT_DIR@". If you give "" no chroot is performed.
.TP
.B username: \fI<name>
If given, after binding the port the user privileges are dropped. Default is
"@UNBOUND_USERNAME@". If you give username: "" no user change is performed. 
.IP
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.
.TP
.B directory: \fI<directory>
Sets the working directory for the program. Default is "@UNBOUND_RUN_DIR@".
.TP
.B logfile: \fI<filename>
If "" is given, logging goes to stderr, or nowhere once daemonized.
The logfile is appended to, in the following format: 
.nf
[seconds since 1970] unbound[pid:tid]: type: message. 
.fi
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.
.TP
.B use\-syslog: \fI<yes or no>
Sets unbound to send log messages to the syslogd, using 
\fIsyslog\fR(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.
.TP
.B log\-time\-ascii: \fI<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.
.TP
.B log\-queries: \fI<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 (significantly) slower.  Odd (nonprintable)
characters in names are printed as '?'.
.TP
.B pidfile: \fI<filename>
The process id is written to the file. Default is "@UNBOUND_PIDFILE@". 
So,
.nf
kill \-HUP `cat @UNBOUND_PIDFILE@` 
.fi
triggers a reload,
.nf
kill \-QUIT `cat @UNBOUND_PIDFILE@` 
.fi
gracefully terminates.
.TP
.B root\-hints: \fI<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.
.TP
.B hide\-identity: \fI<yes or no>
If enabled id.server and hostname.bind queries are refused.
.TP
.B identity: \fI<string>
Set the identity to report. If set to "", the default, then the hostname
of the server is returned.
.TP
.B hide\-version: \fI<yes or no>
If enabled version.server and version.bind queries are refused.
.TP
.B version: \fI<string>
Set the version to report. If set to "", the default, then the package
version is returned.
.TP
.B target\-fetch\-policy: \fI<"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. 
.IP
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. 
.IP
Enclose the list between quotes ("") and put spaces between numbers.
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.
.TP
.B harden\-short\-bufsize: \fI<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.
.TP
.B harden\-large\-queries: \fI<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.
.TP
.B harden\-glue: \fI<yes or no>
Will trust glue only if it is within the servers authority. Default is on.
.TP
.B harden\-dnssec\-stripped: \fI<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.
.TP
.B harden\-below\-nxdomain: \fI<yes or no>
From draft\-vixie\-dnsext\-resimprove, returns nxdomain to queries for a name
below another name that is already known to be nxdomain.  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.
.TP
.B harden\-referral\-path: \fI<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 validation 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 target\-fetch\-policy
to increase the max depth that is checked to.
.TP
.B harden\-algo\-downgrade: \fI<yes or no>
Harden against algorithm downgrade when multiple algorithms are
advertised in the DS record.  If no, allows the weakest algorithm to
validate the zone.  Default is yes.  Zone signers must produce zones
that allow this feature to work, but sometimes they do not, and turning
this option off avoids that validation failure.
.TP
.B use\-caps\-for\-id: \fI<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.
.TP
.B private\-address: \fI<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 \fBlocal\-data\fR
that you configured is allowed to, and you can specify additional
names using \fBprivate\-domain\fR.  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 spamblocklists as they use that.
.TP
.B private\-domain: \fI<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.
.TP
.B unwanted\-reply\-threshold: \fI<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).
.TP
.B do\-not\-query\-address: \fI<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.
.TP
.B do\-not\-query\-localhost: \fI<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.
.TP
.B prefetch: \fI<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.
.TP
.B prefetch-key: \fI<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.
.TP
.B rrset-roundrobin: \fI<yes or no>
If yes, Unbound rotates RRSet order in response (the random number is taken
from the query ID, for speed and thread safety).  Default is no.
.TP
.B minimal-responses: \fI<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.
.TP
.B module\-config: \fI<"module names">
Module configuration, a list of module names separated by spaces, 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.
.TP
.B trust\-anchor\-file: \fI<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.
.TP
.B auto\-trust\-anchor\-file: \fI<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
\fBtrust\-anchor\-file\fR.  The file is written to when the anchor is updated,
so the unbound user must have write permission.
.TP
.B trust\-anchor: \fI<"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 addition 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.
.TP
.B trusted\-keys\-file: \fI<filename>
File with trusted keys for validation. Specify more than one file
with several entries, one file per entry. Like \fBtrust\-anchor\-file\fR
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.
.TP
.B dlv\-anchor\-file: \fI<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
\fItrust\-anchor\-file:\fR 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.
.TP
.B dlv\-anchor: \fI<"Resource Record">
Much like trust\-anchor, this is a DLV anchor with the DS or DNSKEY inline.
.TP
.B domain\-insecure: \fI<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).
.IP
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.
.TP
.B val\-override\-date: \fI<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 verifying RRSIG inception
and expiration dates, instead of the current date. Do not set this unless 
you are debugging signature inception and expiration. The value \-1 ignores
the date altogether, useful for some special applications.
.TP
.B val\-sig\-skew\-min: \fI<seconds>
Minimum number of seconds of clock skew to apply to validated signatures.
A value of 10% of the signature lifetime (expiration \- 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 signatures.
.TP
.B val\-sig\-skew\-max: \fI<seconds>
Maximum number of seconds of clock skew to apply to validated signatures.
A value of 10% of the signature lifetime (expiration \- 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.
.TP
.B val\-bogus\-ttl: \fI<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.
.TP
.B val\-clean\-additional: \fI<yes or no>
Instruct the validator to remove data from the additional section 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.
.TP
.B val\-log\-level: \fI<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.
.TP
.B val\-permissive\-mode: \fI<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". 
.TP
.B ignore\-cd\-flag: \fI<yes or no>
Instruct unbound to ignore the CD flag from clients and refuse to
return bogus answers to them.  Thus, the CD (Checking Disabled) flag
does not disable checking any more.  This is useful if legacy (w2008)
servers that set the CD flag but cannot validate DNSSEC themselves are
the clients, and then unbound provides them with DNSSEC protection.
The default value is "no".
.TP
.B val\-nsec3\-keysize\-iterations: \fI<"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.
.TP
.B add\-holddown: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR 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.
.TP
.B del\-holddown: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR 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.
.TP
.B keep\-missing: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR 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.
.TP
.B key\-cache\-size: \fI<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 kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B key\-cache\-slabs: \fI<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.
.TP
.B neg\-cache\-size: \fI<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).
.TP
.B unblock\-lan\-zones: \fI<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 network 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.
.TP
.B local\-zone: \fI<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, typetransparent, inform, 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.
.IP
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.
.TP 10
\h'5'\fIdeny\fR
Do not send an answer, drop the query.
If there is a match from local data, the query is answered.
.TP 10
\h'5'\fIrefuse\fR
Send an error message reply, with rcode REFUSED.
If there is a match from local data, the query is answered.
.TP 10
\h'5'\fIstatic\fR
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.
.TP 10
\h'5'\fItransparent\fR 
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.
.TP 10
\h'5'\fItypetransparent\fR 
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.
.TP 10
\h'5'\fIredirect\fR 
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.example.com and www.foo.example.com are redirected, so
that users with web browsers cannot access sites with suffix example.com.
.TP 10
\h'5'\fIinform\fR 
The query is answered normally.  The client IP address (@portnumber)
is printed to the logfile.  The log message is: timestamp, unbound-pid,
info: zonename inform IP@port queryname type class.  This option can be
used for normal resolution, but machines looking up infected names are
logged, eg. to run antivirus on them.
.TP 10
\h'5'\fInodefault\fR 
Used to turn off default contents for AS112 zones. The other types
also turn off default contents for the zone. The 'nodefault' option 
has no other effect than turning off default contents for the 
given zone.
.P
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 provide 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.
.TP 10
\h'5'\fIlocalhost\fR 
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:
.nf
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"
.fi
.TP 10
\h'5'\fIreverse IPv4 loopback\fR 
Default content:
.nf
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."
.fi
.TP 10
\h'5'\fIreverse IPv6 loopback\fR 
Default content:
.nf
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."
.fi
.TP 10
\h'5'\fIreverse RFC1918 local use zones\fR 
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 \fBlocal\-zone:\fR is set static and as \fBlocal\-data:\fR SOA and NS 
records are provided.
.TP 10
\h'5'\fIreverse RFC3330 IP4 this, link\-local, testnet and broadcast\fR 
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).
.TP 10
\h'5'\fIreverse RFC4291 IP6 unspecified\fR
Reverse data for zone 
.nf
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.
.fi
.TP 10
\h'5'\fIreverse RFC4193 IPv6 Locally Assigned Local Addresses\fR
Reverse data for zone D.F.ip6.arpa.
.TP 10
\h'5'\fIreverse RFC4291 IPv6 Link Local Addresses\fR
Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
.TP 10
\h'5'\fIreverse IPv6 Example Prefix\fR
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:
.nf
  local\-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
.fi
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.
.\" End of local-zone listing.
.TP 5
.B local\-data: \fI"<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 determines
further processing. If local\-data is configured that is not a subdomain of
a local\-zone, a transparent local\-zone is configured. 
For record types such as TXT, use single quotes, as in 
local\-data: 'example. TXT "text"'.
.IP
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.
.TP 5
.B local\-data\-ptr: \fI"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"
.SS "Remote Control Options"
In the
.B remote\-control:
clause are the declarations for the remote control facility.  If this is
enabled, the \fIunbound\-control\fR(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
\fIunbound\-control\fR(8) utility also reads the \fBremote\-control\fR
section for options.  To setup the correct self\-signed certificates use the
\fIunbound\-control\-setup\fR(8) utility.
.TP 5
.B control\-enable: \fI<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.
.TP 5
.B control\-interface: \fI<ip address or path>
Give IPv4 or IPv6 addresses or local socket path 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.
If you change this and permissions have been dropped, you must restart
the server for the change to take effect.
.TP 5
.B control\-port: \fI<port number>
The port number to listen on for IPv4 or IPv6 control interfaces,
default is 8953.
If you change this and permissions have been dropped, you must restart
the server for the change to take effect.
.TP 5
.B control\-use\-cert: \fI<yes or no>
Whether to require certificate authentication of control connections.
The default is "yes".
This should not be changed unless there are other mechanisms in place
to prevent untrusted users from accessing the remote control
interface.
.TP 5
.B server\-key\-file: \fI<private key file>
Path to the server private key, by default unbound_server.key.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by the unbound server, but not by \fIunbound\-control\fR.
.TP 5
.B server\-cert\-file: \fI<certificate file.pem>
Path to the server self signed certificate, by default unbound_server.pem.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by the unbound server, and also by \fIunbound\-control\fR.
.TP 5
.B control\-key\-file: \fI<private key file>
Path to the control client private key, by default unbound_control.key.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by \fIunbound\-control\fR.
.TP 5
.B control\-cert\-file: \fI<certificate file.pem>
Path to the control client certificate, by default unbound_control.pem.
This certificate has to be signed with the server certificate.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by \fIunbound\-control\fR.
.SS "Stub Zone Options"
.LP
There may be multiple
.B stub\-zone:
clauses. Each with a name: and zero or more hostnames or IP addresses.
For the stub zone this list of nameservers is used. Class IN is assumed.
The servers should be authority servers, not recursors; unbound performs
the recursive processing itself for stub zones.
.P
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 
.B stub\-addr:
<ip address of host[@port]>. 
The unbound resolver can then access the data, without referring to the 
public internet for it. 
.P
This setup allows DNSSEC signed zones to be served by that 
authoritative 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. 
.TP
.B name: \fI<domain name>
Name of the stub zone.
.TP
.B stub\-host: \fI<domain name>
Name of stub zone nameserver. Is itself resolved before it is used.
.TP
.B stub\-addr: \fI<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.
.TP
.B stub\-prime: \fI<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.
.TP
.B stub\-first: \fI<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.
.SS "Forward Zone Options"
.LP
There may be multiple
.B forward\-zone:
clauses. Each with a \fBname:\fR 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 \fBforward\-host:\fR and
\fBforward\-addr:\fR 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 forward\-addr target will
forward all queries to that other server (unless it can answer from
the cache).
.TP
.B name: \fI<domain name>
Name of the forward zone.
.TP
.B forward\-host: \fI<domain name>
Name of server to forward to. Is itself resolved before it is used.
.TP
.B forward\-addr: \fI<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.
.TP
.B forward\-first: \fI<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.
.SS "Python Module Options"
.LP
The
.B python:
clause gives the settings for the \fIpython\fR(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 \fBmodule\-config:\fR option
(usually first, or between the validator and iterator).
.TP
.B python\-script: \fI<python file>\fR
The script file to load. 
.SS "DNS64 Module Options"
.LP
The dns64 module must be configured in the \fBmodule\-config:\fR "dns64
validator iterator" directive and be compiled into the daemon to be
enabled.  These settings go in the \fBserver:\fR section.
.TP
.B dns64\-prefix: \fI<IPv6 prefix>\fR
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.
.TP
.B dns64\-synthall: \fI<yes or no>\fR
Debug option, default no.  If enabled, synthesize all AAAA records
despite the presence of actual AAAA records.
.SH "MEMORY CONTROL EXAMPLE"
In the example config settings below memory usage is reduced. Some service
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 service,
which on BSD\-32bit tops out at 30\-40 Mb after heavy usage. 
.P
.nf
# 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"
.fi
.SH "FILES"
.TP
.I @UNBOUND_RUN_DIR@
default unbound working directory.
.TP
.I @UNBOUND_CHROOT_DIR@
default
\fIchroot\fR(2)
location.
.TP
.I @ub_conf_file@
unbound configuration file.
.TP
.I @UNBOUND_PIDFILE@
default unbound pidfile with process ID of the running daemon.
.TP
.I unbound.log
unbound log file. default is to log to 
\fIsyslog\fR(3). 
.SH "SEE ALSO"
\fIunbound\fR(8), 
\fIunbound\-checkconf\fR(8).
.SH "AUTHORS"
.B Unbound 
was written by NLnet Labs. Please see CREDITS file
in the distribution for further details.