I have two data frames.  The first, df.1, contains two columns of paired numerical identifiers, where each column includes ~100,000 rows.  The second  data frame, df.2, includes one column (df.2$C) of numerical identifiers. This data frame has around 200 rows.
How can I find the paired subset of data of df.1 that includes only the rows with values of the identifiers found in df.2$C? 
The final subset would include the paired data of df.1 which corresponds to identifiers found in df.2$C that match the identifiers found in df.1$A, df.1$B or both.
 
     
    