For incoming calls, the telephone network exchange removes the prefix from the number dialed (destination number). Therefore, the LANCOM only receives the number itself, which may be treated differently depending on the source:
- Numbers from the ISDN network are translated with the ISDN mapping table to the internal number which is entered for the receiving MSN.
- Calls from a SIP network are mapped to the internal destination number entered for the corresponding SIP line.
With the altered number, the Call Manager begins to search the call routing table from top to bottom. If the Call Router cannot find a matching entry there, the call is forwarded directly to the internal number:
| Remote site dials | Call router receives | Assigned via | Number in use | Correct call route | Destination line | |
|---|---|---|---|---|---|---|
| 1 | 0 123 456 789 | 456 789 | internal destination number for SIP line | 11 | None | Internal |
| 2 | 0 123 555 555 1 | 555 555 1 | ISDN mapping | 11 | None | Internal |
| 3 | 0 123 555 555 2 | 555 555 2 | ISDN mapping | 12 | None | Internal |
