It could be installed separately, without installing SQL Server 2016, it is included with SQL Server 2012 Feature Pack. Also, you could download only SQL Native Client 11.msi install file, from this web page: SQL Native Client 11 download page. I went to Installed Programs and verified that SQL Native Client 11 was not installed.
Summary
Instructions provided describe how to ensure that Microsoft SQL Server Native Client (SNaC) is installed on ArcGIS Desktop products. Even when ArcGIS Desktop software has been successfully installed, there can be issues establishing a direct connection to an ArcSDE database or upon opening existing .mxd files or .pmf files where the data sources are broken. One possibility for this behavior could be that the Microsoft SQL Server Native Client is not installed on the client machine(s) attempting to connect to an ArcSDE database, or open an existing .mxd or .pmf file using an ArcSDE direct connection. Beginning with ArcGIS 10, the SQL Server Native Client 2008, a prerequisite to making direct connections to SQL Server, is installed with ArcGIS Desktop, ArcGIS Server, and ArcReader. This can optionally be installed with ArcGIS Engine. What's new for geodatabases in ArcGIS 10 Depending on the options chosen during installation, the Microsoft SQL Server Native Client (SNaC) may not have been installed.
Procedure
Please verify that the following steps have been completed.
On the Windows client machine, in Add / Remove Programs, verify that 'Turn Windows features on or off' has been selected.
Check to see if the Microsoft SQL Server 2008 Native Client has been installed. If the SQL Server 2008 Native Client has already been installed, then do not proceed to step 3 as this may not be the cause of the specific connection issues. If however, the SQL Server 2008 Native Client has not been installed, then proceed to step 3.
Execute the ArcGIS Desktop setup.exe - Application. By deploying the setup.exe, the Microsoft SQL Server Native Client setup is included in the installation. For additional information please review the following link: ArcGIS 10 Enterprise Deployment
Once the SQL Server Native Client has been installed, proceed with establishing an ArcSDE direct connection or open an existing .mxd or .pmf file containing direct connection links to an ArcSDE SQL Server database.
Related Information
Article ID: 000011340
Software: and prior) 10 ArcGIS GeoEvent Server 10 ArcGIS Image Server 10 ArcGIS-ArcEditor 10 ArcGIS-ArcInfo 10 ArcReader 10 ArcSDE 10 ArcGIS Server 10, (10.0