How do I find dups across different columns

[Nyrubi]

I have a spreadsheet where I need to find dups. For instance col 1 will have
an ID but col5 will have name. There can be several instances of the same ID
but with different names in col5. I want to find all the dups across col1
and col5. I am currently using the following formula:
=IF(COUNTIF($A$1:$A$100,A1)>1,"Dup","Not Dup") How can I enhance this to
include looking for dups across column5? Thank you.

 

[JBeaucaire]

There could be different meanings to your question, so I need
clarification

1. Do you want a count of the duplicate IDs in column 1 counted
independently of anything else...PLUS the count of duplicate names i
column 5 counted independently

2. Do you want a count of when the ID and Name in a single row i
duplicated somewhere else, also paired together

 

[JBeaucaire]

To only get DUP when both the ID and the Name are duplicated TOGETHE
somewhere else, this would accomplish that

=IF(SUMPRODUCT(--($F$1:$F$100=F1),--($A$1:$A$100=A1))>1,"Dup","No Dup"

 

[Khoshravan]

Why you don't use your formula for column 5?