ltm monitor dns¶

ltm monitor dns(1) BIG-IP TMSH Manual ltm monitor dns(1)

NAME
dns - Configures a Domain Name System (DNS) monitor.

MODULE
ltm monitor

SYNTAX
Configure the dns component within the ltm monitor module using the syntax in the following sections.

CREATE/MODIFY
create dns [name]
modify dns [name]
options:
accept-rcode [no-error | anything]
adaptive [enabled | disabled]
adaptive-divergence-type [relative | absolute]
adaptive-divergence-value [integer]
adaptive-limit [integer]
adaptive-sampling-timespan [integer]
answer-contains [query-type | any-type | anything]
app-service [[string] | none]
defaults-from [name]
description [string]
destination [ [ ipv4 address[:port] ] | [ ipv6 address[.port] ] ]
interval [integer]
manual-resume [enabled | disabled]
qname [string]
qtype [a | aaaa]
recv [none | [string] ]
reverse [enabled | disabled]
time-until-up [integer]
timeout [integer]
transparent [disabled | enabled]
up-interval [integer]

edit dns [ [ [name] | [glob] | [regex] ] ... ]
options:
all-properties
non-default-properties

DELETE
delete dns [name]

Note: You cannot delete default monitors.

RUN
run dns [name] [ destination [ [ ipv4 address[:port] ] | [ ipv6 address[.port] ] ] ]

STOP
stop dns [name]

DESCRIPTION
You can use the dns component to configure a custom monitor. This type of monitor verifies the DNS service by
attempting to send DNS requests generated using the parameters provided to a pool, pool member, or virtual
server and validating the DNS response.

You can test a custom monitor configuration against a specified target destination by using the run command,
and view the results of such a test by using the show command with the test-result option.

The following user roles (in addition to the root user) have permissions to run and stop an ltm monitor test:

admin, application-editor, manager, operator, resource-admin

EXAMPLES
create dns my_dns defaults-from dns qname www.test.com

Creates a monitor named my_dns that inherits properties other than qname from the default DNS monitor.

list dns

Displays the properties of all of the DNS monitors.

run dns my_dns destination 10.10.10.10:80

Runs a one-shot test of the custom monitor my_dns against a target node at 10.10.10.10:80.

stop dns my_dns

Cancels a one-shot test of the custom monitor my_dns in progress.

show dns my_dns test-result

Displays the result of the most recent one-shot test of the custom monitor my_dns.

OPTIONS
accept_rcode
Specifies the RCODE required in the response for an 'up' status. The default value is no-error.

The options are:

no-error
Specifies that the status of the node will be marked up if the received dns message has RCODE =
NOERROR.

anything
Specifies that the status of the node will be marked up irrespective of the RCODE in the dns message
received.

adaptive
Specifies whether the adaptive feature is enabled for this monitor. Not all monitors support the adaptive
feature.

adaptive-divergence-type
Specifies whether the adaptive-divergence-value is relative or absolute.

adaptive-divergence-value
Specifies how far from mean latency each monitor probe is allowed to be. If adaptive-divergence-type is
relative, this value is a percentage deviation from mean (e.g. 50 would indicate the probe is allowed to
exceed the mean latency by 50%.) If adaptive-divergence-type is absolute, this value is an offset from
mean in milliseconds (e.g. 250 would indicate the probe is allowed allowed to exceed the mean latency by
250 ms.) A probe that exceeds latency is counted the same as a probe that is not received, so in the
typical scenario, it will require three missed latencies in a row to mark a pool member or node down
(i.e. a 15-second interval with a 46-second timeout, would require three missed probes before the pool
member or node would be marked down.)

adaptive-limit
Specifies the hard limit, in milliseconds, which the probe is not allowed to exceed, regardless of the
divergence value. For example, if this value is 500, then the probe latency may not exceed 500 ms even if
that would still fall within the divergence value.

adaptive-sampling-timespan
Specifies the size of the sliding window, in seconds, which records probe history. For example, if this
value is 300, then a sliding window of the last five minutes' probe history will be used for calculating
probe mean latency and standard deviation.

answer_contains
Specifies the record types required in the answer section of the response in order to mark the status of
a node up. The default value is query-type.

The options are:

query-type
Specifies that the response should contain at least one answer of which the resource record type
matches the qtype.

any-type
Specifies that the dns message should contain at least one answer.

anything
Specifies that an empty answer section is enough to mark the status of the node up.

app-service
Specifies the name of the application service to which the monitor belongs. The default value is none.
Note: If the strict-updates option is enabled on the application service that owns the object, you cannot
modify or delete the monitor. Only the application service can modify or delete the monitor.

defaults-from
Specifies the name of the monitor from which you want your custom monitor to inherit settings. The
default value is dns.

description
User defined description.

destination
Specifies the IP address and service port of the resource that is the destination of this monitor.
Possible values are:

*:* Specifies to perform a health check on the IP address and port supplied by a pool member.

*:port
Specifies to perform a health check on the server with the IP address supplied by the pool member
and the port you specify.

IP address:port
Specifies to mark a pool member up or down based on the response of the server at the IP address and
port you specify.

IP address:port (with the transparent option enabled)
Specifies to perform a health check on the server at the IP address and port you specify, route the
check through the IP address and port supplied by the pool member, and mark the pool member (the
gateway) up or down accordingly.

This option is required for the command run, unless an IP address and service port are specified in the
destination option for the specified custom monitor.

glob Displays the items that match the glob expression. See help glob for a description of glob expression
syntax.

interval
Specifies, in seconds, the frequency at which the system issues the monitor check when either the
resource is down or the status of the resource is unknown. The default value is 5 seconds.

Important: F5 Networks recommends that when you configure this option and the up-interval option,
whichever value is greater be a multiple of the lesser value to allow for an even distribution of monitor
checks among all monitors.

manual-resume
Specifies whether the system automatically changes the status of a resource to up at the next successful
monitor check. The default value of the manual-resume option is disabled.

Note that if you set the manual-resume option to enabled, you must manually mark the resource as up
before the system can use it for load balancing connections.

name Specifies a unique name for the component. This option is required for the commands create, delete,
modify, run and stop.

partition
Displays the administrative partition within which the component resides.

qname
Specifies the query name that the monitor send a DNS query for. The default value is Enter a query name.

qtype
Specifies the query type of that the monitor sends a query. The default value is a.

The options are:

a Specifies that the monitor will send a DNS query of type A.

aaaa Specifies that the monitor will send a DNS query of type AAAA.

recv Specifies the ip address that the monitor looks for in the dns response's resource record sections. The
ip address should be specified in the dotted-decimal notation or ipv6 notation. The default value is
none. If no recv value is specified, then the dns message will be checked against accept_rcode and
answer_contains monitor parameters respectively.

regex
Displays the items that match the regular expression. The regular expression must be preceded by an at
sign (@[regular expression]) to indicate that the identifier is a regular expression. See help regex for
a description of regular expression syntax.

reverse
Specifies whether the monitor operates in reverse mode. When the monitor is in reverse mode, a successful
receive string match marks the monitored object down instead of up. You can use the this mode only if you
configure recv option.

The default value is disabled, which specifies that the monitor does not operate in reverse mode. The
enabled value specifies that the monitor operates in reverse mode.

test-result
Displays the result of the most recent one-shot test of the specified monitor(s), if any such test has
been performed since BIG-IP was started.

time-until-up
Specifies the amount of time, in seconds, after the first successful response before a node is marked up.
A value of 0 (zero) causes a node to be marked up immediately after a valid response is received from the
node. The default value is 0 (zero).

timeout
Specifies the number of seconds the target has in which to respond to the monitor request. The default
value is 16 seconds. If the target responds within the set time period, it is considered up. If the
target does not respond within the set time period, it is considered down. Also, if the target responds
with a RESET packet, the system immediately flags the target as down without waiting for the timeout
interval to expire.

transparent
Specifies whether the monitor operates in transparent mode. Monitors in transparent mode can monitor pool
members through firewalls. The default value is disabled.

up-interval
Specifies, in seconds, the frequency at which the system issues the monitor check when the resource is
up. The default value is 0 (zero), which specifies that the system uses the value of the interval option
whether the resource is up or down.

Important: F5 Networks recommends that when you configure this option and the interval option, whichever
value is greater be a multiple of the lesser value to allow for an even distribution of monitor checks
among all monitors.

SEE ALSO
create, delete, edit, glob, list, modify, regex, run, show, stop, tmsh

COPYRIGHT
No part of this program may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or information storage and retrieval systems, for any purpose
other than the purchaser's personal use, without the express written permission of F5 Networks, Inc.

BIG-IP 2017-08-16 ltm monitor dns(1)