Hello,
Please check here for the P-bit:
The ISIS Link State PDU Format - Routing TCP IP (ccexpert.us)
P is the Partition Repair bit. Although the bit exists in both L1 and L2 LSPs, it is relevant only in L2 LSPs. When this bit is set, it indicates that the originating router supports the automatic repair of area partitions. Cisco IOS does not support this function, so the P bit of LSPs originated by Cisco routers will always be zero.
Cisco IOS IP Routing: ISIS Command Reference - Integrated IS-IS Commands: L through V [Support] - Cisco
Table 16 has the triggers and their meanings. (search for word "triggers" on page)
Table 11 also has the P bit information which is stated above. CISCO and other vendors do not support it.
-David
