Using Transparent Network IP Resolution with the ODBC Driver
TransparentNetworkIPResolution is a revision of the existing MultiSubnetFailover feature, available starting with 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 | Behavior |
|---|---|---|
| (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 |
Enabled, Disabled |
Enabled |
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. |