SqlBulkCopyColumnMapping

I am performing a SQLBulkCopy which is working fine except I would like to get some info on SqlBulkCopyColumnMapping. I have 2 columns that are being mapped out of 20, the other 18 columns match up and don't require SqlBulkCopyColumnMapping to be used. So after mapping my 2 columns and running my script I noticed that the only data that was copied between tables was the 2 columns that were mapped, not the other 18. Does this mean I have to map ALL columns so that all of the data can be copied or is there a way to tell SQLBulkCopy that the rest of the columns already match up and just copy them?

I am working in ASP.Net/VB and below is a sampling of the code I have

Using bulkCopy As SqlBulkCopy = New SqlBulkCopy(destinationConnection)
            bulkCopy.DestinationTableName = "dbo.WebProxyLog"
 
            Dim mapTime1 As New SqlBulkCopyColumnMapping("logTime", "logDate")
            bulkCopy.ColumnMappings.Add(mapTime1)
            Dim mapTime2 As New SqlBulkCopyColumnMapping("logTime", "logTime")
            bulkCopy.ColumnMappings.Add(mapTime2)
            bulkCopy.BulkCopyTimeout = 2000
 
            Try
                bulkCopy.WriteToServer(reader)
 
            Catch ex As Exception
                Console.WriteLine(ex.Message)
 
            Finally
                reader.Close()
            End Try
        End Using

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