DNM Modification rules are looked at in a very specific order. This order is maintained within the Number Modification library and is roughly as follows:
The highest priority rules are rules that involve specific endpoints.
The next highest priority goes to rules that apply to all private networking endpoints (SIP and SIP-Q) (endpoint = ALL-PN)
Then next highest priority goes to rules that apply to all endpoints (i.e. excluding the subscribers) (endpoint = ALL)
Lowest priority goes to rules that apply to endpoints and subscribers (endpoint = NONE)
Within each of the above categories, priorities are assigned as follows:
Specific numbering plan rules have higher priority than business group specific rules
Business group specific rules have higher priority than system wide rules.
The terminating context has higher priority than the originating context
Priorities are also assigned to the Input Type Of Number (specific gets higher priority than an ANY rule). Up to 3 ANY Input Type Of Number rules (prioritized 1 to 3) can be specified that take an output type of number that is not ANY. The output type of number ANY automatically receives reserved priority number 4. The priorities 1 to 4 will also apply to the rules with a defined input type of number.
It is not possible to enter 2 modification rules with the same number source field value that only differ on priority.
An ANY (input) / INT (output) / 1 (priority) / Input Number (Number Source) rule precludes creating an ANY (input) / INT (output) / 2 (priority) or 3 (priority) / Input Number (Number Source) rule.
In the Telephony Control Server Assistant, Number Modification rules are shown in order of priority from highest priority to lowest priority. When analyzing a problem in Number Modification, an administrator can then easily find out which rule is not behaving correctly and can then correct the problem.
Fallback rules apply when a higher priority rule fails. The number modification library does not necessarily fail anymore when the first or second matching rule does not deliver a result. Instead the next best rule is searched and applied until either no rules are available anymore or a rule ends up into a positive modification.
Parent topic: Display Number Modifications Table