How to import around 150MB(more than 25 lac rows) notepad file in Excel 2013

I personally would not choose to process such large files with VBA - as you have hinted I would pre-process the text file (I would use C# as my preference) to produce a CSV file that could then just be loaded directly into Excel.

However, you have tagged VBA and you have also said that you are not familiar with it, so here is a simple method of loading your file using VBA.
You will need to add in specific information about which parts of the file you want and where to put them in the spreadsheet. Unfortunately you haven't given us enough detail, but hopefully I've made it clear what goes where - look out for "TODO:"

Note: This is not very performant. There are also more elegant ways of doing this but I'm trying to keep it simple.

1. Create the code that follows in a module in Excel (Alt-F11 will bring up the Visual Basic editor. In the left-hand pane you will see your workbook name, right-click on that and select "Insert" then select "Module"

2. You are going to open your text file and read it line by line. For each line you will determine whether or not it is required (or can be discarded), if so then you will copy data from the line into the spreadsheet ... here is the code to read the file from end to end

Sub ReadFile()

    Dim fileName As String
        
    Close   'close any open files
        
    'TODO: Change this line to locate your file
    fileName = "c:\temp\example.txt"
    
    Dim fileNum As Integer
    fileNum = FreeFile
    
    Open fileName For Input As #fileNum
    Dim aLine As String
    Dim rowNum As Integer
    
    rowNum = 3  'TODO: the row number you want the data to start on
    
    Do While Not EOF(fileNum)
    
        Line Input #fileNum, aLine
        If WantLine(aLine) Then ProcessTheLine aLine, rowNum
   
    Loop
    Close #fileNum

End Sub

3. The function WantLine will determine whether or not you can ignore the line or whether you want to process it ...

Function WantLine(aLine As String) As Boolean

    Dim retValue As Boolean
    retValue = False

    If Mid$(aLine, 1, 12) = "MAC Address:" Then retValue = True
    If Mid$(aLine, 1, 12) = "Port       :" Then retValue = True
    If Mid$(aLine, 1, 12) = "TimeStamp  :" Then retValue = True

    'TODO: Insert other checks here

    WantLine = retValue
End Function

4. The subroutine ProcessTheLine starts pulling a line of text apart for the data ...

Sub ProcessTheLine(aLine As String, rowNum As Integer)

    If Mid$(aLine, 1, 12) = "MAC Address:" Then
        'MAC Address will appear in column 1(A)
        'The actual data starts in column 14 for a max of 15 chars
        SetDataForCol 1, rowNum, aLine, 14, 15
        'VLAN/VSI/SI will appear in column 2(B)
        'The actual data starts in column 49 for a max of 20 chars
        SetDataForCol 2, rowNum, aLine, 49, 20
    End If

    If Mid$(aLine, 1, 12) = "Port       :" Then
        SetDataForCol 3, rowNum, aLine, 14, 15
        SetDataForCol 4, rowNum, aLine, 49, 20
    End If

    'TODO: ... etc. Insert code to process the other types of data. Change the locations of the data above if necessary

    'increment the row only when we've processed a "block"
    'note this only works if "Timestamp" is a required line in WantLine
    If Mid$(aLine, 1, 12) = "TimeStamp  :" Then rowNum = rowNum + 1

End Sub

5.Finally, the subroutine SetDataForCol will extract the data from the line at the position provided for the length provided and insert it into the spreadsheet at the location provided

Sub SetDataForCol(col As Integer, rowNum As Integer, aLine As String, start As Integer, slen As Integer)
    Dim data As String
    data = Trim$(Mid$(aLine, start, slen))
    'TODO: You might need to select a sheet or workbook here depending on your needs
    Cells(rowNum, col) = data
End Sub