Using Transparent Network IP Resolution

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TransparentNetworkIPResolution is a revision of the existing MultiSubnetFailover feature, available in Microsoft ODBC Driver 13.1 for SQL Server, that affects the connection sequence of the driver in the case where the first resolved IP of the hostname does not respond and there are multiple IPs associated with the hostname. It interacts with MultiSubnetFailover to provide the following three connection sequences:

  • 0: One IP is attempted, followed by all IPs in parallel
  • 1: All IPs are attempted in parallel
  • 2: All IPs are attempted one after another
TransparentNetworkIPResolution MultiSubnetFailover Behaviour
(default) (default) 0
(default) Enabled 1
(default) Disabled 0
Enabled (default) 0
Enabled Enabled 1
Enabled Disabled 0
Disabled (default) 2
Disabled Enabled 1
Disabled Disabled 2

The TransparentNetworkIPResolution connection string and DSN keyword controls this setting at the connection-string level. The default is enabled.

Keyword Values Default
TransparentNetworkIPResolution Yes, No Yes

The SQL_COPT_SS_TNIR pre-connection attribute allows an application to control this setting programmatically:

Connection Attribute Size/Type Default Value Description
SQL_COPT_SS_TNIR (1249) SQL_IS_INTEGER or SQL_IS_UINTEGER SQL_IS_ON(1), SQL_IS_OFF(0) SQL_IS_ON Enables or disables TNIR.

For more information about MultiSubnetFailover, see ODBC Driver on Linux and macOS - High Availability and Disaster Recovery

See Also