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dns parameter

The following operations can be performed on "dns parameter":

set | unset | show

set dns parameter

Modifies global DNS parameters on the NetScaler appliance.

Synopsys

set dns parameter [-retries <positive_integer>] [-minTTL <secs>] [-maxTTL <secs>] [-nameLookupPriority ( WINS | DNS )] [-recursion ( ENABLED | DISABLED )] [-resolutionOrder <resolutionOrder>] [-dnssec ( ENABLED | DISABLED )] [-maxPipeline <positive_integer>] [-dnsRootReferral ( ENABLED | DISABLED )] [-dns64Timeout <msecs>]

Arguments

retries

Maximum number of retry attempts when no response is received for a query sent to a name server. Applies to end resolver and forwarder configurations.

Default value: 5

Minimum value: 1

Maximum value: 5

minTTL

Minimum permissible time to live (TTL) for all records cached in the DNS cache by DNS proxy, end resolver, and forwarder configurations. If the TTL of a record that is to be cached is lower than the value configured for minTTL, the TTL of the record is set to the value of minTTL before caching. When you modify this setting, the new value is applied only to those records that are cached after the modification. The TTL values of existing records are not changed.

Maximum value: 604800

maxTTL

Maximum time to live (TTL) for all records cached in the DNS cache by DNS proxy, end resolver, and forwarder configurations. If the TTL of a record that is to be cached is higher than the value configured for maxTTL, the TTL of the record is set to the value of maxTTL before caching. When you modify this setting, the new value is applied only to those records that are cached after the modification. The TTL values of existing records are not changed.

Default value: 604800

Minimum value: 1

Maximum value: 604800

nameLookupPriority

Type of lookup (DNS or WINS) to attempt first. If the first-priority lookup fails, the second-priority lookup is attempted. Used only by the SSL VPN feature.

Possible values: WINS, DNS

Default value: WINS

recursion

Function as an end resolver and recursively resolve queries for domains that are not hosted on the NetScaler appliance. Also resolve queries recursively when the external name servers configured on the appliance (for a forwarder configuration) are unavailable. When external name servers are unavailable, the appliance queries a root server and resolves the request recursively, as it does for an end resolver configuration.

Possible values: ENABLED, DISABLED

Default value: DISABLED

resolutionOrder

Type of DNS queries (A, AAAA, or both) to generate during the routine functioning of certain NetScaler features, such as SSL VPN, cache redirection, and the integrated cache. The queries are sent to the external name servers that are configured for the forwarder function. If you specify both query types, you can also specify the order. Available settings function as follows:

  • OnlyAQuery. Send queries for IPv4 address records (A records) only.

  • OnlyAAAAQuery. Send queries for IPv6 address records (AAAA records) instead of queries for IPv4 address records (A records).

  • AThenAAAAQuery. Send a query for an A record, and then send a query for an AAAA record if the query for the A record results in a NODATA response from the name server.

  • AAAAThenAQuery. Send a query for an AAAA record, and then send a query for an A record if the query for the AAAA record results in a NODATA response from the name server.

Possible values: OnlyAQuery, OnlyAAAAQuery, AThenAAAAQuery, AAAAThenAQuery

Default value: OnlyAQuery

dnssec

Enable or disable the Domain Name System Security Extensions (DNSSEC) feature on the appliance. Note: Even when the DNSSEC feature is enabled, forwarder configurations (used by internal NetScaler features such as SSL VPN and Cache Redirection for name resolution) do not support the DNSSEC OK (DO) bit in the EDNS0 OPT header.

Possible values: ENABLED, DISABLED

Default value: ENABLED

maxPipeline

Maximum number of concurrent DNS requests to allow on a single client connection, which is identified by the <clientip:port>-<vserver ip:port> tuple. A value of 0 (zero) applies no limit to the number of concurrent DNS requests allowed on a single client connection.

Default value: NSNATPCB_MAXPIPELINE

Minimum value: 0

dnsRootReferral

Send a root referral if a client queries a domain name that is unrelated to the domains configured/cached on the NetScaler appliance. If the setting is disabled, the appliance sends a blank response instead of a root referral. Applicable to domains for which the appliance is authoritative. Disable the parameter when the appliance is under attack from a client that is sending a flood of queries for unrelated domains.

Possible values: ENABLED, DISABLED

Default value: DISABLED

dns64Timeout

While doing DNS64 resolution, this parameter specifies the time to wait before sending an A query if no response is received from backend DNS server for AAAA query.

Default value: -1

Maximum value: 10000

unset dns parameter

Use this command to remove dns parameter settings.Refer to the set dns parameter command for meanings of the arguments.

Synopsys

unset dns parameter [-retries] [-minTTL] [-maxTTL] [-nameLookupPriority] [-recursion] [-resolutionOrder] [-dnssec] [-maxPipeline] [-dnsRootReferral] [-dns64Timeout]

show dns parameter

Displays the global DNS parameters.

Synopsys

show dns parameter

Outputs

retries

Maximum number of retry attempts when no response is received for a query sent to a name server. Applies to end resolver and forwarder configurations.

minTTL

Minimum permissible time to live (TTL) for all records cached in the DNS cache by DNS proxy, end resolver, and forwarder configurations. If the TTL of a record that is to be cached is lower than the value configured for minTTL, the TTL of the record is set to the value of minTTL before caching. When you modify this setting, the new value is applied only to those records that are cached after the modification. The TTL values of existing records are not changed.

maxTTL

Maximum time to live (TTL) for all records cached in the DNS cache by DNS proxy, end resolver, and forwarder configurations. If the TTL of a record that is to be cached is higher than the value configured for maxTTL, the TTL of the record is set to the value of maxTTL before caching. When you modify this setting, the new value is applied only to those records that are cached after the modification. The TTL values of existing records are not changed.

nameLookupPriority

Type of lookup (DNS or WINS) to attempt first. If the first-priority lookup fails, the second-priority lookup is attempted. Used only by the SSL VPN feature.

cacheRecords

Cache resource records in the DNS cache. Applies to resource records obtained through proxy configurations only. End resolver and forwarder configurations always cache records in the DNS cache, and you cannot disable this behavior. When you disable record caching, the appliance stops caching server responses. However, cached records are not flushed. The appliance does not serve requests from the cache until record caching is enabled again.

recursion

Function as an end resolver and recursively resolve queries for domains that are not hosted on the NetScaler appliance. Also resolve queries recursively when the external name servers configured on the appliance (for a forwarder configuration) are unavailable. When external name servers are unavailable, the appliance queries a root server and resolves the request recursively, as it does for an end resolver configuration.

resolutionOrder

Type of DNS queries (A, AAAA, or both) to generate during the routine functioning of certain NetScaler features, such as SSL VPN, cache redirection, and the integrated cache. The queries are sent to the external name servers that are configured for the forwarder function. If you specify both query types, you can also specify the order. Available settings function as follows:

  • OnlyAQuery. Send queries for IPv4 address records (A records) only.

  • OnlyAAAAQuery. Send queries for IPv6 address records (AAAA records) instead of queries for IPv4 address records (A records).

  • AThenAAAAQuery. Send a query for an A record, and then send a query for an AAAA record if the query for the A record results in a NODATA response from the name server.

  • AAAAThenAQuery. Send a query for an AAAA record, and then send a query for an A record if the query for the AAAA record results in a NODATA response from the name server.

dnssec

Enable or disable the Domain Name System Security Extensions (DNSSEC) feature on the appliance. Note: Even when the DNSSEC feature is enabled, forwarder configurations (used by internal NetScaler features such as SSL VPN and Cache Redirection for name resolution) do not support the DNSSEC OK (DO) bit in the EDNS0 OPT header.

maxPipeline

Maximum value of the concurrent DNS pipeline. A setting of zero makes the pipeline infinite

dnsRootReferral

Send a root referral if a client queries a domain name that is unrelated to the domains configured/cached on the NetScaler appliance. If the setting is disabled, the appliance sends a blank response instead of a root referral. Applicable to domains for which the appliance is authoritative. Disable the parameter when the appliance is under attack from a client that is sending a flood of queries for unrelated domains.

dns64Timeout

While doing DNS64 resolution, this parameter specifies the time to wait before sending an A query if no response is received from backend DNS server for AAAA query.

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