Two variations of this procedure can occur.
For received duplicate prefix-SID indexes or labels for different prefixes within the same IGP instance, the router does the following:
programs ILM/NHLFE for the first prefix
logs a trap and a syslog error message
does not program the subsequent prefix in the datapath
For received duplicate prefix-SID indexes for different prefixes across IGP instances, there are two options:
In the global SID index range mode of operation, the resulting ILM label values are the same across the IGP instances. The router does the following:
programs ILM/NHLFE for the prefix of the winning IGP instance based on the RTM route type preference
logs a trap and a syslog error message
does not program the subsequent prefix SIDs in the datapath
In the per-instance SID index range mode of operation, the resulting ILM label will have different values across the IGP instances. The router programs ILM/NHLFE for each prefix as expected.