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Outgoing Calls Fail Because the Minimum or Maximum Number Length Is Incorrectly Configured for the Outgoing Call Prefix

Publication Date:  2015-07-24 Views:  124 Downloads:  0
Issue Description
Version: U1980 V100R001C01SPC800

Network: PSTN–(TUP)–U1980–(TUP)–Router

When an outer-office mobile phone user dials 8568291 (number of a phone under the router), the called number is sent to the U1980 using SS7. The U1980 deletes the first four digits from the called number and sends the changed number to the router. The mobile phone user hears an announcement indicating that the called number does not exist.

The customer considers that: with the first four digits deleted, the called number is changed to 291 and sent to the AR2220 through office route 4 (matching prefix 8568291 whose minimum and maximum lengths are 7). In addition, prefix 291 is available for routing calls from U1980 users to AR2220 users through office route 4. Both the minimum and maximum number lengths for prefix 291 are 3. According to the customer's imagination, when an incoming call to number 8568291 enters the U1980, the called number matches prefix 8568291. After the first four digits are deleted, the change number matches prefix 291. Therefore, the call can be connected to the router.
Handling Process
Step 1 Check the prefixes. It is found that the customer has configured local prefix 8568291 whose minimum and maximum number lengths are 7, and local prefix 291 whose minimum and maximum number lengths are 3.

Step 2 Change the minimum number length of prefix 8568291 to 3, and retains the maximum number length (that is, 7).

The fault is rectified.

----End

Root Cause
Prefixes are incorrectly configured.
Suggestions
 When configuring number change, ensure that the number lengths before and after number change are greater than or equal to the minimum number length, and less than or equal to the maximum number length. (Assume that the number length before number change is A, and the number length after number change is B. A and B must meet the following conditions: minimum number length ≤ A ≤ maximum number length, minimum number length ≤ B ≤ maximum number length)

 Except the prefix for routing based on the number length, for which the system performs number analysis again based on the result of routing based on the number length, the system will not perform number analysis again based on the number change result of other common prefixes.

END