DELV(1) BIND9 DELV(1)
delv - DNS lookup and validation utility
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 [queryopt...] [query...]
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
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
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).
A typical invocation of delv looks like:
delv @server name type
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
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).
is the domain name to be looked up.
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.
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
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
Sets the source IP address of the query to address. This 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
Sets the query class for the requested data. Currently, only class
"IN" is supported in delv and any other value is ignored.
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
Display the delv help usage output and exit.
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
Enables memory usage debugging.
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.
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).
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.
The default query type is "A", unless the -x option is supplied to
indicate a reverse lookup, in which case it is "PTR".
Print the delv version and exit.
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 184.108.40.206.in-addr.arpa and sets the query type to PTR. IPv6
addresses are looked up using nibble format under the IP6.ARPA
Forces delv to only use IPv4.
Forces delv to only use IPv6.
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:
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.
Controls whether to display the CLASS when printing a record. The
default is to display the CLASS.
Controls whether to display the TTL when printing a record. The
default is to display the TTL.
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).
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).
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).
Provide a terse answer. The default is to print the answer in a
Toggle the display of comment lines in the output. The default is
to print comments.
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.
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
Controls whether to display the trust level when printing a record.
The default is to display the trust level.
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.
Set or clear the display options +[no]comments, +[no]rrcomments,
and +[no]trust as a group.
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.
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
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.
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.
dig(1), named(8), RFC4034, RFC4035, RFC4431, RFC5074, RFC5155.
Internet Systems Consortium, Inc.
Copyright (C) 2014-2016 Internet Systems Consortium, Inc. ("ISC")
ISC 2014-04-23 DELV(1)