Cisco Cisco IOS Software Release 12.2(33)SXH
PIM Triggered Joins
Information About PIM Triggered Joins
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Cisco IOS Release 12.2(33)SXH
Figure 1
Operation of PIM Triggered Joins During a Switchover
The mechanics of the PIM Triggered Joins feature are as follows:
•
In steady state, PIM neighbors exchange periodic PIM hello messages.
•
An active supervisor engine receives PIM joins to periodically refresh mroute states.
•
When an active supervisor engine fails, the standby supervisor engine takes over to become the new
active supervisor engine.
active supervisor engine.
•
PIM neighbors on the new active supervisor engine then modify the GenID value and send the new
GenID in PIM hello messages to adjacent PIM neighbors as a means to alert adjacent PIM neighbors
that PIM forwarding has been restarted.
GenID in PIM hello messages to adjacent PIM neighbors as a means to alert adjacent PIM neighbors
that PIM forwarding has been restarted.
•
Adjacent PIM neighbors that receive PIM hello messages on an interface with a new GenID then
send PIM triggered joins for all (*, G) and (S, G) mroutes that use that interface as an RPF interface,
promptly reestablishing those states on the newly active supervisor engine.
send PIM triggered joins for all (*, G) and (S, G) mroutes that use that interface as an RPF interface,
promptly reestablishing those states on the newly active supervisor engine.
Prior to the introduction of the PIM Triggered Joins feature in Cisco IOS Release 12.2(33)SXH, in the
event of a supervisor engine switchover on a Catalyst 6500 series switch, all hardware entries would have
been suspended until the control plane was reestablished. States for mroutes on the new active supervisor
engine, thus, would not have been rebuilt until the periodic joins sent by adjacent PIM neighbors were
received by PIM neighbors on the new active supervisor engine. The PIM Triggered Joins feature, thus,
improves the recovergence time of mroutes after a supervisor engine switchover, enabling mroute states
to be rebuilt promptly after a supervisor engine switchover.
event of a supervisor engine switchover on a Catalyst 6500 series switch, all hardware entries would have
been suspended until the control plane was reestablished. States for mroutes on the new active supervisor
engine, thus, would not have been rebuilt until the periodic joins sent by adjacent PIM neighbors were
received by PIM neighbors on the new active supervisor engine. The PIM Triggered Joins feature, thus,
improves the recovergence time of mroutes after a supervisor engine switchover, enabling mroute states
to be rebuilt promptly after a supervisor engine switchover.
Note
If a PIM neighbor is unable to process the GenID value, the PIM neighbor will ignore the GenID value
and behave in the manner that it would prior to the introduction of the PIM Triggered Joins feature in
Cisco IOS Release 12.2(33)SXH.
and behave in the manner that it would prior to the introduction of the PIM Triggered Joins feature in
Cisco IOS Release 12.2(33)SXH.
Standby
Active
RP
Triggered PIM Joins
Hello with new GenID
Periodic PIM Joins
Periodic PIM Hellos
230523
Failure!