There are five operating PIM modes:
- PIM Dense Mode (PIM-DM)
- PIM Spare Mode (PIM-SM)
- PIM Spare Dense Mode
- PIM Source Specific Multicast (PIM-SSM)
- PIM Bidirectional Mode (Bidir-PIM)
PIM Control messages are sent using IP Protocol 103. Register and register stop messages can be sent using unicast, or multicast with a time-to-live of 1 to all PIM routers at address 224.0.0.13
| ID | Type | Destination | PIM Protocol |
| 0 | Hello | 224.0.0.13 (all PIM routers) | PIM-SM, PIM-DM, Bidir-PIM, SSM |
| 1 | Register | RP address (Unicast) | PIM-SM |
| 2 | Register Stop | First-hop router (Unicast) | PIM-SM |
| 3 | Join/prune | 224.0.0.13 | PIM-SM, Bidir-PIM, SSM |
| 4 | Bootstrap | 224.0.0.13 | PIM-SM, Bidir-PIM |
| 5 | Assert | 224.0.0.13 | PIM-SM, PIM-DM, Bidir-PIM |
| 8 | Candidate RP Advertisement | Bootstrap router (BSR) address (Unicast) | PIM-SM, Bidir-PIM |
| 9 | State Refresh | 224.0.0.13 | PIM-DM |
| 10 | DF Election | 224.0.0.13 | Bidir-PIM |
Hello messages are sent every 30 seconds out PIM-Enabled interfaces.
Hello messages serve other purposes such as to elect a designated router and to form additional features.
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