| User | Dials | Correct call route | Correct user | Mapping, number in use | Destination line | |
|---|---|---|---|---|---|---|
| 1 | VoIP phone, branch | 212 | None | VoIP softphone | 212 | Internal |
| 2 | VoIP phone, branch | 199 | 4 # | SIP subscribers at the headquarters | #: 199 | SIP-PBX |
| 3 | VoIP phone, branch | 0 555 555 | 3 0# | 0241#: 0241 555 555 | ISDN | |
| 4 | VoIP phone, branch | 0 0123 666 666 | 2 00# | 00#: 0123 666 666 | SIP-PBX |
- Internal call between two VoIP terminal devices at the branch office. The dialed number 212 does not match any of the routes listed in the call routing table. Therefore, the call router searches the local user list, finds the correct entry there and can forward the call internally.
- Internal call between a VoIP terminal device at the branch office and the internal subscriber 199 at the headquarters. The dialed number 199 does not match any of the routes listed in the call routing table during the first pass. Similarly, no matching entry can be found in the local user list. In the second pass through the call routing table, the default routes are considered too. The route with the called number # (4) corresponds to all calls which could not be assigned earlier. The call to 199 is therefore conducted over the SIP PBX line.
- External call from the branch office into the local telephone network. The dialed number 0 555 555 matches the route 0# (3) in the call routing table. The call router removes the 0 outside-line access prefix, adds the area code for the local telephone network and makes the call to 0241 555 555 via the ISDN line.
- External call from the branch office into a national telephone network. The dialed number 0 555 555 matches the route 00# (2) in the call routing table. The call router directs the call to the SIP PBX line unchanged. Only now does the SIP PBX remove the 0 outside-line access prefix and directs the call to 0123 555 555 via the ISDN exchange line.
