5.20.4.1. Network with Open Numbering; Alternate Routing with Complete Set
of Prefix Codes 
Figure 47. Alternate Routing with a set of Prefix Codes
Routes to node 040 are configured in NODENO 010:
- Route with route code 94 with first trunk group and PREFDGT1=9394
- Route with route code 94 with second trunk group and PREFDGT1=9794 (alternate routing
trunk
group)
Station A dials 944711;in NODENO 010 the dialing of 94 leads to DAR=TIE.A loop can be formed if, for example, both trunks to NODENO 040 develop a malfunction or are overloaded, or if a failure occurs in node 040. An alternate routing trunk group is then seized in NODENO 030, in this case via NODENO 050, 060 and 070. all number 9697944711 is transmitted on the trunk from NODENO 030 to NODENO 050, since the alternate routing trunk group (route code=94) is configured with PREFDGT1=969794.If the message is received at NODENO 070 (call number = 944711), it is established that the direct trunk group for route code 94 is unavailable. The alternative trunk group with PREFDGT1=9394 is seized on the trunk to NODENO 020. The loop, comprising the 5 nodes NODENO 030, 050, 060, 070 and 020, is now closed. All available B channels are seized in turn.The loop can be prevented by restricting the permissible connections (AMO KNMAT). In NODENO 050 all connections from source node NODENO 010 to destination node NODENO 040 are prohibited. The configured routes (1st and 2nd trunk groups) can both still be used. Stations connected to other nodes (e.g. station C, NODENO 100) can also use the transit route via 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;