The routing rules created by the routing tables can be overridden at several levels.
Tariff level overrides
When you prepare a tariff, you can specify that a smaller subset of the carriers be used for Least Cost Routing than the full set of carriers returned by the Routing tables. You can also specify that one carrier not in the routing tables be selected as the only carrier for the call. For more information, please study Preparing a tariff.
You can also override standard routing immediately for particular tariffs. These changes are implemented using a set of web pages on the DUAL Softswitch Administration System and remain in force until the next scheduled tariff change is brought into effect. As such, this feature would normally only be used in reaction to real-time routing issues where rerouting should only be considered for customers on specific tariffs.
Blocked Routes are rules that prohibit calls being sent to specific carriers based on those calls destinations and tariffs. They are retained when a new routing table is brought into service and can be modified online using the DUAL Softswitch Administrative Control Panel. Blocked Routes only apply to calls where Least Cost Routing is in use.