IP SLAs DNS Operation

Feature History for IP SLAs - DNS Operation

This table provides release and platform support information for the features explained in this module.

These features are available in all the releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature Name and Description

Supported Platform
Cisco IOS XE 17.18.1

IP SLAs - DNS Operation: This operation measures the time difference between sending a DNS request and receiving a reply.

Cisco C9350 Series Smart Switches

Cisco C9610 Series Smart Switches

IP SLAs DNS

The IP SLAs DNS operation is designed to measure the time difference between sending a DNS request and receiving a reply. By analyzing the results of the DNS operation, network administrators can determine the DNS lookup time, which is a crucial factor in assessing the performance of DNS or web servers. Monitoring DNS response times helps identify potential issues and ensures optimal performance for applications that rely on fast and reliable domain name resolution.

How IP SLAs DNS works

Summary

The DNS operation measures the time difference between sending a DNS request and receiving a reply, providing valuable insight into DNS server responsiveness. DNS plays a critical role on the Internet by translating network node names into IP addresses. With the IP SLAs DNS operation, a device can query for an IP address when a host name is provided, or query for a host name when an IP address is specified, allowing comprehensive monitoring of DNS resolution performance.

In the figure below Device B is configured as the source IP SLAs device and a DNS operation is configured with the DNS server as the destination device.

Workflow

Figure 1. DNS Operation

Connection response time is computed by measuring the difference between the time taken to send a request to the DNS server and the time a reply is received by Device B. The resulting DNS lookup time can help you analyze your DNS performance.

Faster DNS lookup times translate to a faster web server access experience.

Guidelines to to configure IP SLAs DNS

  • If the IP Service Level Agreements (SLAs) operation is not running and not generating statistics, add the verify-data command to the configuration (while configuring in IP SLA configuration mode) to enable data verification. When data verification is enabled, each operation response is checked for corruption. Use the verify-data command with caution during normal operations because it generates unnecessary overhead.

  • Use the debug ip sla trace and debug ip sla error commands to help troubleshoot issues with an IP SLAs operation.

  • There is no need to configure an IP SLAs responder on the destination device.

Configure an IP SLAs DNS operation on the source device

Follow the steps in each of these tasks to configure an IP SLAs DNS operation on the source device.

Before you begin

There is no need to configure an IP SLAs responder on the destination device.

Procedure

Step 1

Perform any one of these tasks:

Step 2

Schedule IP SLAs operations

Configure a basic DNS operation on the source device

Perform this task to configure a basic DNS operation on the source device.

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip sla operation-number

Example:

Device(config)# ip sla 10

Starts configuring an IP SLAs operation and enters IP SLA configuration mode.

Step 4

dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]

Example:

Device(config-ip-sla)# dns host1 name-server 172.20.2.132

Defines a DNS operation and enters IP SLA DNS configuration mode.

Step 5

frequency seconds

Example:

Device(config-ip-sla-dns)# frequency 90

(Optional) Sets the rate at which a specified IP SLAs operation repeats.

Step 6

end

Example:

Device(config-ip-sla-dns)# end

Exits to privileged EXEC mode.

Configure a DNS operation with optional parameters on the source device

Perform this task to configure a DNS operation with optional parameters on the source device.

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip sla operation-number

Example:

Device(config)# ip sla 10

Starts configuring an IP SLAs operation and enters IP SLA configuration mode.

Step 4

dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]

Example:

Device(config-ip-sla)# dns host1 name-server 172.20.2.132

Defines a DNS operation and enters IP SLA DNS configuration mode.

  • destination-ip-address : The IP address to query for its host name (reverse lookup).

  • destination-hostname : The host name to query for its IP address (standard lookup).

  • name-server ip-address : The IP address of the DNS server to be used for the query.

  • source-ip {ip-address | hostname} : (Optional) Specifies the source IP address or hostname for the request.

  • source-port port-number : (Optional) Specifies the source port number for the DNS request.

Step 5

history buckets-kept size

Example:

Device(config-ip-sla-dns)# history buckets-kept 25

(Optional) Sets the number of history buckets that are kept during the lifetime of an IP SLAs operation.

Step 6

history distributions-of-statistics-kept size

Example:

Device(config-ip-sla-dns)# history distributions-of-statistics-kept 5

(Optional) Sets the number of statistics distributions kept per hop during an IP SLAs operation.

Step 7

history enhanced [interval seconds] [buckets number-of-buckets]

Example:

Device(config-ip-sla-dns)# history enhanced interval 900 buckets 100

(Optional) Enables enhanced history gathering for an IP SLAs operation.

  • interval seconds : (Optional) The time interval, in seconds, between each statistics recording.

  • buckets number-of-buckets : (Optional) The number of history data buckets (records) to store for the operation.

Step 8

history filter {none | all | overThreshold | failures}

Example:

Device(config-ip-sla-dns)# history filter failures

(Optional) Defines the type of information kept in the history table for an IP SLAs operation.

Step 9

frequency seconds

Example:

Device(config-ip-sla-dns)# frequency 30

(Optional) Sets the rate at which a specified IP SLAs operation repeats.

Step 10

history hours-of-statistics-kept hours

Example:

Device(config-ip-sla-dns)# history hours-of-statistics-kept 4

(Optional) Sets the number of hours for which statistics are maintained for an IP SLAs operation.

Step 11

history lives-kept lives

Example:

Device(config-ip-sla-dns)# history lives-kept 5

(Optional) Sets the number of lives maintained in the history table for an IP SLAs operation.

Step 12

owner owner-id

Example:

Device(config-ip-sla-dns)# owner admin

(Optional) Configures the Simple Network Management Protocol (SNMP) owner of an IP SLAs operation.

Step 13

history statistics-distribution-interval milliseconds

Example:

Device(config-ip-sla-dns)# history statistics-distribution-interval 10

(Optional) Sets the time interval for each statistics distribution kept for an IP SLAs operation.

Step 14

tag text

Example:

Device(config-ip-sla-dns)# tag TelnetPollServer1

(Optional) Creates a user-specified identifier for an IP SLAs operation.

Step 15

threshold milliseconds

Example:

Device(config-ip-sla-dns)# threshold 10000

(Optional) Sets the upper threshold value for calculating network monitoring statistics created by an IP SLAs operation.

Step 16

timeout milliseconds

Example:

Device(config-ip-sla-dns)# timeout 10000

(Optional) Sets the amount of time an IP SLAs operation waits for a response from its request packet.

Step 17

end

Example:

Device(config-ip-sla-dns)# end

Exits to privileged EXEC mode.

Schedule IP SLAs operations

Perform this task to schedule IP SLAs operations.

Before you begin

  • All IP SLAs operations to be scheduled must be already configured.

  • The frequency of all operations scheduled in a multioperation group must be the same.

  • The list of one or more operation ID numbers to be added to a multioperation group must be limited to a maximum of 125 characters in length, including commas (,).

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip sla schedule operation-number [life {forever | seconds}] [start-time {[hh:mm:ss] [month day | day month] | pending | now | after hh:mm:ss}] [ageout seconds] [recurring]

Example:

Device(config)# ip sla schedule 10 life forever start-time
OR
Device(config)# ip sla schedule 1 3,4,6-9 schedule-period 50 frequency range 80-100

(Optional) Configures the scheduling parameters for an individual IP SLAs operation.

  • operation-number : The IP SLA operation number to schedule (must match a previously created IP SLA operation).

    The range is from 1 to 2147483647.

  • life {forever | seconds} : How long the operation will run.

    • forever : Runs the operation continuously until manually stopped.

    • seconds : Number of seconds the operation should run.

      The range is from 1 to 2147483647 seconds.

  • start-time {[hh:mm:ss] [month day | day month] | pending | now | after hh:mm:ss} : Specifies when to start the operation.

    • hh:mm:ss [month day | day month] : Specific time and date.

    • pending : Waits for a manual start.

    • now : Starts immediately.

    • after hh:mm:ss : Starts after the specified amount of time.

  • ageout seconds : Time (in seconds) after which the operation is automatically deleted.

    The range is from 0 to 2147483647 seconds.

  • recurring : Makes the operation run repeatedly according to its frequency settin

Step 4

ip sla group schedule group-operation-number operation-id-numbers {schedule-period schedule-period-range |schedule-together}[ageout seconds] frequency group-operation-frequency [life {forever | seconds}] [start-time {hh:mm [:ss] [month day | day month] | pending | now | after hh:mm[:ss]}]

Example:


Device(config)# ip sla group schedule 10 schedule-period frequency
OR
Device(config)# ip sla group schedule 1 3,4,6-9 life forever start-time now

(Optional) Specifies an IP SLAs operation group number and the range of operation numbers for a multioperation scheduler.

  • group-operation-number : The number assigned to the group operation (must be unique).

    The range is from 1 to 2147483647.

  • operation-id-numbers : List of individual IP SLA operation numbers to be included in the group.

    The range is from 1 to 2147483647 (can be a series separated by spaces).

  • schedule-period schedule-period-range: Schedules each operation in the group with a specified time period between them.

    The range is from 1 to 604800 (seconds; up to 7 days).

  • schedule-together : Starts all operations in the group at the same time.

  • frequency group-operation-frequency : How often (in seconds) the group operation runs.

    The range is from 1 to 604800 seconds.

Step 5

end

Example:

Device(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Configuration example for a DNS operation

The following example shows how to configure a DNS operation from Device B to the DNS server (IP address 172.20.2.132) as shown in the “DNS Operation” figure in the “DNS Operation” section. The operation is scheduled to start immediately. In this example, the target address is a hostname and the DNS operation will query the DNS server for the IP address associated with the hostname host1. No configuration is required at the DNS server

Device B Configuration

Device> enable
Device# configure terminal
Device(config)# ip sla 11
Device(config-ip-sla)# dns host1 name-server 172.20.2.132
Device(config-ip-sla)# frequency 50
Device(config-ip-sla)# timeout 8000
Device(config-ip-sla)# tag DNS-Test
Device(config-ip-sla)# exit
Device(config-ip-sla)# ip sla schedule 11 start-time now

Verify IP SLA operations

Command

Description

show ip sla group schedule

Displays IP SLAs group schedule details.

show ip sla configuration

Displays IP SLAs configuration details.