Embodiments of the present invention include a method for processing a non-normalized local exchange routing guide (LERG) table to produce a normalized LERG table. The LERG tables have an NPA field, an NXX field, a Block_Id field, and a Switch_Id field. The method includes joining all distinct combinations of NPA and NXX in the non-normalized LERG table to all valid Block_Ids to produce a NormLERG table. The method further includes populating a Switch_Id field, in each NormLERG record having a distinct NPA-NXX value. The populating of the Switch_Id field is based on a number of corresponding non-normalized LERG records and on the Switch_Id field in one of the corresponding non-normalized LERG records and on a number of distinct Switch_ID values in the corresponding non-normalized LERG records. Each of the corresponding non-normalized LERG records has a same one of the NPA-NXX values.