Vlookup not functioning properly

[ADziver]

Can someone explain to me why vlookup is producing this behavior:
   A              B             C              D          E

cat	1			cat
dog	2			dog
bird	3			bird
mouse	4			mouse
Test 1		Test 2
1		1
2		2
#N/A		#N/A
4		4

In Test 1, the lookup value is taken from the reference range.  The formula in cell A9 is: =VLOOKUP(A3,$A$1:$B$4,2)
In Test 2, the lookup value is taken from a separate range
The Formula in cell C9 is: =VLOOKUP(E3,$A$1:$B$4,2)

Why do I get a #N/A error?

Thank you for help on this matter. 

[#2 · Accepted solution]

@ADziver 

I think so you have to use the last parameter of =Vlookup as 0. So then it will work properly.

[#3]

That seems to fix the problem. I thought that the last parameter could be omitted. Thank you for the response.