no-bidirectional-mode
Syntax
no-birectional-mode;
Hierarchy Level
[edit logical-systems logical-system-name protocols pim graceful-restart], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim graceful-restart], [edit protocols pim graceful-restart], [edit routing-instances routing-instance-name protocols pim graceful-restart]
Description
Disable forwarding for bidirectional PIM routes during graceful restart recovery, both in cases of a routing protocol process (rpd) restart and graceful Routing Engine switchover.
Bidirectional PIM accepts packets for a bidirectional route on multiple interfaces. This means that some topologies might develop multicast routing loops if all PIM neighbors are not synchronized with regard to the identity of the designated forwarder (DF) on each link. If one router is forwarding without actively participating in DF elections, particularly after unicast routing changes, multicast routing loops might occur.
If graceful restart for PIM is enabled and the forwarding of packets on bidirectional routes is disallowed (by including the no-bidirectional-mode statement in the configuration), PIM behaves conservatively to avoid multicast routing loops during the recovery period. When the routing protocol process (rpd) restarts, all bidirectional routes are deleted. After graceful restart has completed, the routes are re-added, based on the converged unicast and bidirectional PIM state. While graceful restart is active, bidirectional multicast flows drop packets.
Default
If graceful restart for PIM is enabled and the bidirectional PIM is enabled, the default graceful restart behavior is to continue forwarding packets on bidirectional routes. If the gracefully restarting router was serving as a DF for some interfaces to rendezvous points, the restarting router sends a DF Winner message with a metric of 0 on each of these RP interfaces. This ensures that a neighbor router does not become the DF due to unicast topology changes that might occur during the graceful restart period. Sending a DF Winner message with a metric of 0 prevents another PIM neighbor from assuming the DF role until after graceful restart completes. When graceful restart completes, the gracefully restarted router sends another DF Winner message with the actual converged unicast metric.
Graceful Routing Engine switchover operates independently of the graceful restart behavior. If graceful Routing Engine switchover is configured without graceful restart, all PIM routes for all modes are deleted when the rpd process restarts. If graceful Routing Engine switchover is configured with graceful restart, the behavior is the same as described here, except that the recovery happens on the Routing Engine that assumes primary role.
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Release Information
Statement introduced in Junos OS Release 12.1.