backoff-period
Syntax
backoff-period milliseconds;
Hierarchy Level
[edit logical-systems logical-system-name protocols pim interface (Protocols PIM) interface-name bidirectional df-election], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim interface (Protocols PIM) interface-name bidirectional df-election], [edit protocols pim interface (Protocols PIM) interface-name bidirectional df-election], [edit routing-instances routing-instance-name protocols pim interface (Protocols PIM) interface-name bidirectional df-election]
Description
Configure the designated forwarder (DF) election backoff period for bidirectional PIM. The backoff-period statement configures the period that the acting DF waits between receiving a better DF Offer and sending the Pass message to transfer DF responsibility.
Junos OS checks rendezvous point (RP) unicast reachability before accepting incoming DF messages. DF messages for unreachable rendezvous points are ignored. This is needed to prevent the following example scenario. Routers A and B are downstream routers on the same LAN, and both are supposed to send DF election messages with an infinite metric on their upstream interfaces (reverse-path forwarding [RPF] interfaces). Router A has a higher IP address than Router B. When both routers lose the path to the RP, both send an Offer message with the infinite metric onto the LAN. Router A wins the election because it has a higher IP address, and Router B backs off as a result. After three Offer messages, according to RFC 5015, Router A looks up the RP and finds no path to the RP. As a result, Router A transitions to the Lose state and sends nothing. On the other hand, after backing off for an interval of 3 x the Offer period, Router B does not receive any messages, and resumes the DF election by sending a new Offer message. Hence, the pattern repeats indefinitely.
Options
milliseconds—Period that the acting DF waits between receiving a better DF Offer and sending the Pass message to transfer DF responsibility.
Range: 100 through 65,535 milliseconds
Default: 1000
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.