5.20.4.2. Network with Open Numbering; Alternate Routing with one Prefix
Code 
Figure 48. Alternate Routing with one Prefix Code
In this case a single fault can produce a loop. The reason is that
only the node code of the destination node is supplied as the prefix
code. In each transit node the path to the next transit node in the direction
of the destination is redefined. Routes to node 040 are configured in
NODENO 010:
- Route with route code 94 with first trunk group and PREFDGT1=94
- Route with route code 94 with second trunk group and PREFDGT1=94 (alternate routing
trunk group)
Station A dials 944711. In NODENO 010 the dialing of 94 again leads to DAR=TIE. Call number 944711 is sent to NODENO 020, where route code 94 is also assigned with PREFDGT1=94, with the result that call number 944711 is transmitted to NODENO 030. Here a direct trunk group is configured for route code 94 (no prefix). The number forwarded to NODENO 040 is thus 4711.With this configuration a loop may occur if, for example, the trunk from NODENO 030 to NODENO 040 has a fault. An alternative trunk group, e.g. via NODENO 050, is then used in NODENO 030. From here a trunk group can then be seized in the direction of NODENO 030 or an alternative trunk group via NODEO 020. In either case a loop is formed. This can be prevented by means of a prohibition criterion in NODENO 050:
- Example Method 1 - command in NODENO 050:
CHA-KNMAT:LEVEL=0,SNNO=10,DNNO=40,CONN=D;
- Example Method 3- command in NODENO 050:
ADD-KNLCR:SNNO=10,DNNO=40,REDSLCOS=1&&64;