# DNS Client Configuration Mode Commands

The DNS Client Configuration Mode is used to manage the system’s DNS interface and caching parameters.

IMPORTANT:

The commands or keywords/variables that are available are dependent on platform type, product version, and installed license(s).
bind

Binds the DNS client to a pre-configured logical IP interface.
Platform:

ASR 5000
Product:

MME, SCM, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    bind { address ip_address [ port number ] | query-over-gtp }

    no bind address

no

Removes the binding of the client to a specified interface.
bind address ip_address

Specifies the IP address of the interface to which the DNS client is being bound in IPv4 dotted-decimal notation.
bind port number

Specifies the UDP port number of the interface to which the DNS client is being bound as an integer from 1 to 65535. Default: 6011
bind query-over-gtp

Specifies that DNS client query is to be performed over GTP.
Usage:

Use this command to associated the client with a specific logical IP address.
Example:
The following command binds the DNS client to a logical interface with an IP address of 10.2.3.4 and a port number of 6000:

    bind address 10.2.3.4
    port 6000

cache algorithm

Configures the method of use for the DNS VPN and session cache.
Platform:

ASR 5000
Product:

MME, SCM, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    cache algorithm { central | local } { FIFO | LRU | LFU }

    default cache algorithm { central | local }

default

Sets the DNS VPN and session cache method to default setting.
central | local

central: Specifies the central proclet (VPN manager)

local: Specifies the local proclet (session manager)
FIFO | LRU | LFU

FIFO: First in first out. This is the default setting for the central proclet.

LRU: Least recently used. This is the default value for the local proclet.

LFU: Least frequently used.
Usage:

Use this command to configure the method by which entries are added and removed from the DNS cache.
Example:
The following command configures the cache algorithm for the central proclet to least frequently used (LFU):

    cache algorithm central lfu

cache size

Configures the maximum number of entries allowed in the DNS cache.
Platform:

ASR 5000
Product:

MME, SCM, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    cache size { central | local } max_size

    default cache size { central | local }

default

Sets the maximum number of entries allowed in the DNS cache to default setting.
{ central | local } max_size

central max_size: Specifies the maximum number of entries allowed in the central proclet cache as an integer from 100 through 65535. Default: 50000.

local max_size: Specifies the maximum number of entries allowed in the local proclet cache as an integer from 100 through 65535. Default: 1000.
Usage:

Use this command to configure the maximum number of entries allowed in the DNS cache.
Example:
The following command configures the cache size of the central proclet to 20000:

    cache size central
    20000

cache ttl

Configures the DNS cache time to live (TTL) for positive and negative responses.
Platform:

ASR 5000
Product:

MME, SCM, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    cache ttl { negative | positive } seconds

    default cache ttl { negative | positive }

    no cache [ ttl { negative | positive } ]

no

Disables any or all configured DNS cache parameters.
default

Sets the DNS cache time to live for positive and negative responses to the default setting.
{ negative | positive } seconds

negative seconds: Specifies the time to live for negative responses as an integer from 60 through 86400. Default: 60.

positive seconds: Specifies the time to live for positive responses. as an integer from 60 through 86400. Default: 86400 (1 day).
Usage:

Use this command to adjust the DNS cache time to live.
Example:
The following commands set the TTL DNS cache to 90 seconds for negative responses and 43200 seconds for positive responses:

    cache ttl negative
    90

    cache ttl positive
    43200

case-sensitive

Configures the case sensitivity requirement for responses to DNS requests.
Platform:

ASR 5000
Product:

MME, SCM, SGSN
Privilege:

Administrator
Syntax

    [ default | no ] case-sensitive response

default

Returns the command to its default setting of disabled.
no

Disables the requirement for case sensitivity in DNS responses.
case-sensitive response

Enables the requirement for case sensitivity in DNS responses.
Usage:

Use this command to require case sensitivity (identical case usage between request and response) on all responses to DNS request messages.
end

Exits the current configuration mode and returns to the Exec mode.
Product:

All
Privilege:

Security Administrator, Administrator
Syntax

    end

Usage:

Use this command to return to the Exec mode.
exit

Exits the current mode and returns to the parent configuration mode.
Product:

All
Privilege:

Security Administrator, Administrator
Syntax

    exit

Usage:

Use this command to return to the parent configuration mode.
resolver

Configures the number of DNS query retries and the retransmission interval once the response timer expires.
Platform:

ASR 5000
Product:

MME, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    resolver { number-of-retries retries | retransmission-interval
     time }

    default { number-of-retries | retransmission-interval }

default

Resets the specified resolver configuration to the default.
number-of-retries retries

Configures the number of DNS query retries on DNS response timeout as an integer from 0 through 4. Default: 2.
retransmission-interval time

Configures the initial retransmission interval (in seconds) for retransmission after the DNS response timeout as an integer from 2 to 5. Default is 3 seconds. The retransmission interval doubles after each retry when only one server is configured. In case both primary and secondary servers are configured, the retransmission time is doubled for the last retry.
Usage:

Set the DNS retransmission retries or the retransmission interval. Issue the command twice to configure both parameters, one-at-a-time.
Example:
The following command sets the DNS resolver retries to 4:

    resolver number-of-retries
    4

round-robin answers

Configures the DNS client to return the DNS results in round-robin fashion if multiple results are available for a DNS query.
Platform:

ASR 5000
Product:

MME, SGSN
Privilege:

Security Administrator, Administrator
Syntax

    [ no | default ] round-robin-answers

no

Removes the configured round robin method for DNS answer.
default

Disables the round robin method for DNS answer.
round-robin-answers

Enables the round robin method for DNS answer.
Usage:

Use this command to configure the DNS client to return the DNS results in round-robin fashion if multiple results are available for a DNS query.
Example:
The following command configures the DNS client to use round robin method for DNS query answers:

    default ] round-robin-answers