delv(1)
DELV(1) BIND9 DELV(1)
NAME
delv - DNS lookup and validation utility
SYNOPSIS
delv [@server] [-4] [-6] [-a anchor-file] [-b address]
[-c class] [-d level] [-i] [-m] [-p port#] [-q name]
[-t type] [-x addr] [name] [type] [class] [queryopt...]
delv [-h]
delv [-v]
delv [queryopt...] [query...]
DESCRIPTION
delv (Domain Entity Lookup & Validation) is a tool for
sending DNS queries and validating the results, using the
the same internal resolver and validator logic as named.
delv will send to a specified name server all queries needed
to fetch and validate the requested data; this includes the
original requested query, subsequent queries to follow CNAME
or DNAME chains, and queries for DNSKEY, DS and DLV records
to establish a chain of trust for DNSSEC validation. It does
not perform iterative resolution, but simulates the behavior
of a name server configured for DNSSEC validating and
forwarding.
By default, responses are validated using built-in DNSSEC
trust anchors for the root zone (".") and for the ISC DNSSEC
lookaside validation zone ("dlv.isc.org"). Records returned
by delv are either fully validated or were not signed. If
validation fails, an explanation of the failure is included
in the output; the validation process can be traced in
detail. Because delv does not rely on an external server to
carry out validation, it can be used to check the validity
of DNS responses in environments where local name servers
may not be trustworthy.
Unless it is told to query a specific name server, delv will
try each of the servers listed in /etc/resolv.conf. If no
usable server addresses are found, delv will send queries to
the localhost addresses (127.0.0.1 for IPv4, ::1 for IPv6).
When no command line arguments or options are given, delv
will perform an NS query for "." (the root zone).
SIMPLE USAGE
A typical invocation of delv looks like:
delv @server name type
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where:
server
is the name or IP address of the name server to query.
This can be an IPv4 address in dotted-decimal notation
or an IPv6 address in colon-delimited notation. When the
supplied server argument is a hostname, delv resolves
that name before querying that name server (note,
however, that this initial lookup is not validated by
DNSSEC).
If no server argument is provided, delv consults
/etc/resolv.conf; if an address is found there, it
queries the name server at that address. If either of
the -4 or -6 options are in use, then only addresses for
the corresponding transport will be tried. If no usable
addresses are found, delv will send queries to the
localhost addresses (127.0.0.1 for IPv4, ::1 for IPv6).
name
is the domain name to be looked up.
type
indicates what type of query is required - ANY, A, MX,
etc. type can be any valid query type. If no type
argument is supplied, delv will perform a lookup for an
A record.
OPTIONS
-a anchor-file
Specifies a file from which to read DNSSEC trust
anchors. The default is /etc/bind.keys, which is
included with BIND 9 and contains trust anchors for the
root zone (".") and for the ISC DNSSEC lookaside
validation zone ("dlv.isc.org").
Keys that do not match the root or DLV trust-anchor
names are ignored; these key names can be overridden
using the +dlv=NAME or +root=NAME options.
Note: When reading the trust anchor file, delv treats
managed-keys statements and trusted-keys statements
identically. That is, for a managed key, it is the
initial key that is trusted; RFC 5011 key management is
not supported. delv will not consult the managed-keys
database maintained by named. This means that if either
of the keys in /etc/bind.keys is revoked and rolled
over, it will be necessary to update /etc/bind.keys to
use DNSSEC validation in delv.
-b address
Sets the source IP address of the query to address. This
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must be a valid address on one of the host's network
interfaces or "0.0.0.0" or "::". An optional source port
may be specified by appending "#<port>"
-c class
Sets the query class for the requested data. Currently,
only class "IN" is supported in delv and any other value
is ignored.
-d level
Set the systemwide debug level to level. The allowed
range is from 0 to 99. The default is 0 (no debugging).
Debugging traces from delv become more verbose as the
debug level increases. See the +mtrace, +rtrace, and
+vtrace options below for additional debugging details.
-h
Display the delv help usage output and exit.
-i
Insecure mode. This disables internal DNSSEC validation.
(Note, however, this does not set the CD bit on upstream
queries. If the server being queried is performing
DNSSEC validation, then it will not return invalid data;
this can cause delv to time out. When it is necessary to
examine invalid data to debug a DNSSEC problem, use dig
+cd.)
-m
Enables memory usage debugging.
-p port#
Specifies a destination port to use for queries instead
of the standard DNS port number 53. This option would be
used with a name server that has been configured to
listen for queries on a non-standard port number.
-q name
Sets the query name to name. While the query name can be
specified without using the -q, it is sometimes
necessary to disambiguate names from types or classes
(for example, when looking up the name "ns", which could
be misinterpreted as the type NS, or "ch", which could
be misinterpreted as class CH).
-t type
Sets the query type to type, which can be any valid
query type supported in BIND 9 except for zone transfer
types AXFR and IXFR. As with -q, this is useful to
distinguish query name type or class when they are
ambiguous. it is sometimes necessary to disambiguate
names from types.
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The default query type is "A", unless the -x option is
supplied to indicate a reverse lookup, in which case it
is "PTR".
-v
Print the delv version and exit.
-x addr
Performs a reverse lookup, mapping an addresses to a
name. addr is an IPv4 address in dotted-decimal
notation, or a colon-delimited IPv6 address. When -x is
used, there is no need to provide the name or type
arguments. delv automatically performs a lookup for a
name like 11.12.13.10.in-addr.arpa and sets the query
type to PTR. IPv6 addresses are looked up using nibble
format under the IP6.ARPA domain.
-4
Forces delv to only use IPv4.
-6
Forces delv to only use IPv6.
QUERY OPTIONS
delv provides a number of query options which affect the way
results are displayed, and in some cases the way lookups are
performed.
Each query option is identified by a keyword preceded by a
plus sign (+). Some keywords set or reset an option. These
may be preceded by the string no to negate the meaning of
that keyword. Other keywords assign values to options like
the timeout interval. They have the form +keyword=value. The
query options are:
+[no]cdflag
Controls whether to set the CD (checking disabled) bit
in queries sent by delv. This may be useful when
troubleshooting DNSSEC problems from behind a validating
resolver. A validating resolver will block invalid
responses, making it difficult to retrieve them for
analysis. Setting the CD flag on queries will cause the
resolver to return invalid responses, which delv can
then validate internally and report the errors in
detail.
+[no]class
Controls whether to display the CLASS when printing a
record. The default is to display the CLASS.
+[no]ttl
Controls whether to display the TTL when printing a
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record. The default is to display the TTL.
+[no]rtrace
Toggle resolver fetch logging. This reports the name and
type of each query sent by delv in the process of
carrying out the resolution and validation process: this
includes including the original query and all subsequent
queries to follow CNAMEs and to establish a chain of
trust for DNSSEC validation.
This is equivalent to setting the debug level to 1 in
the "resolver" logging category. Setting the systemwide
debug level to 1 using the -d option will product the
same output (but will affect other logging categories as
well).
+[no]mtrace
Toggle message logging. This produces a detailed dump of
the responses received by delv in the process of
carrying out the resolution and validation process.
This is equivalent to setting the debug level to 10 for
the the "packets" module of the "resolver" logging
category. Setting the systemwide debug level to 10 using
the -d option will produce the same output (but will
affect other logging categories as well).
+[no]vtrace
Toggle validation logging. This shows the internal
process of the validator as it determines whether an
answer is validly signed, unsigned, or invalid.
This is equivalent to setting the debug level to 3 for
the the "validator" module of the "dnssec" logging
category. Setting the systemwide debug level to 3 using
the -d option will produce the same output (but will
affect other logging categories as well).
+[no]short
Provide a terse answer. The default is to print the
answer in a verbose form.
+[no]comments
Toggle the display of comment lines in the output. The
default is to print comments.
+[no]rrcomments
Toggle the display of per-record comments in the output
(for example, human-readable key information about
DNSKEY records). The default is to print per-record
comments.
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+[no]crypto
Toggle the display of cryptographic fields in DNSSEC
records. The contents of these field are unnecessary to
debug most DNSSEC validation failures and removing them
makes it easier to see the common failures. The default
is to display the fields. When omitted they are replaced
by the string "[omitted]" or in the DNSKEY case the key
id is displayed as the replacement, e.g. "[ key id =
value ]".
+[no]trust
Controls whether to display the trust level when
printing a record. The default is to display the trust
level.
+[no]split[=W]
Split long hex- or base64-formatted fields in resource
records into chunks of W characters (where W is rounded
up to the nearest multiple of 4). +nosplit or +split=0
causes fields not to be split at all. The default is 56
characters, or 44 characters when multiline mode is
active.
+[no]all
Set or clear the display options +[no]comments,
+[no]rrcomments, and +[no]trust as a group.
+[no]multiline
Print long records (such as RRSIG, DNSKEY, and SOA
records) in a verbose multi-line format with
human-readable comments. The default is to print each
record on a single line, to facilitate machine parsing
of the delv output.
+[no]dnssec
Indicates whether to display RRSIG records in the delv
output. The default is to do so. Note that (unlike in
dig) this does not control whether to request DNSSEC
records or whether to validate them. DNSSEC records are
always requested, and validation will always occur
unless suppressed by the use of -i or +noroot and
+nodlv.
+[no]root[=ROOT]
Indicates whether to perform conventional
(non-lookaside) DNSSEC validation, and if so, specifies
the name of a trust anchor. The default is to validate
using a trust anchor of "." (the root zone), for which
there is a built-in key. If specifying a different trust
anchor, then -a must be used to specify a file
containing the key.
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+[no]dlv[=DLV]
Indicates whether to perform DNSSEC lookaside
validation, and if so, specifies the name of the DLV
trust anchor. The default is to perform lookaside
validation using a trust anchor of "dlv.isc.org", for
which there is a built-in key. If specifying a different
name, then -a must be used to specify a file containing
the DLV key.
FILES
/etc/bind.keys
/etc/resolv.conf
SEE ALSO
dig(1), named(8), RFC4034, RFC4035, RFC4431, RFC5074,
RFC5155.
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright 8c9 2014-2016 Internet Systems Consortium, Inc.
("ISC")
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