| User | dials | correct call route | correct user | mapping, number in use | Destination line | |
|---|---|---|---|---|---|---|
| Branch VoIP telephone | 212 | None | VoIP softphone | 212 | Internal | |
| Branch VoIP telephone | 199 | # | SIP subscribers at the headquarters | #: 199 | SIP PBX | |
| Branch VoIP telephone | 0 555 555 | 0# | 0241#: 0241 555 555 | ISDN | ||
| Branch VoIP telephone | 0 0123 666 666 | 00# | 00#: 0123 666 666 | SIP PBX |
- Internal call between two VoIP terminal devices at the branch office. The number dialed, '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 number dialed, '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 standard routes are considered too. The route with the number called '#' corresponds to all calls which could not be assigned earlier. The call to '199' is therefore carried out over the SIP PBX line.
- External call from the branch office into the local telephone network. The number dialed, '0 555,555', matches the route '0#' in the call routing table. The call router removes the '0' outside-line access prefix, completes the area code for the local telephone network and completes the call to '0241 555 555' using the ISDN line.
- External call from the branch office into a national telephone network. The number dialed, '0 0123 555 555', matches the route '00#' in the call routing table. The call router sends the call out to the SIP PBX line unchanged. Only now does the SIP PBX removes the '0' outside-line access prefix and completes the call to '0123 555 555' via the ISDN outside line.