Thanks for all the suggestions, McMurdoStation, I considered them all but I was also using this data for filling other thing which I would like to keep the nulls and I would to change the minimum amount of code possible so I took a different approach. Instead of removing the null rows I selectively added rows that were not null. Here is my solution:

ipList = ds.Tables("RouterIPs").Clone
        'add only non-null ip_addr dropdownlist view
        Dim i As Integer
        Dim dr As DataRow
        For i = 0 To (ds.Tables("RouterIPs").Rows.Count - 1)
            If Not ds.Tables("RouterIPs").Rows(i).Item("IP_Addr") Is DBNull.Value Then
                ipList.ImportRow(ds.Tables("RouterIPs").Rows(i))
            End If
        Next