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Note: The permanent forwarding state must exist on all routers in the path for fast source switchover to function properly. |
The forwarding-cache statement enables you to configure the forwarding cache properties of entries defined by a flow map. You can specify a timeout of never to make the forwarding entries permanent, or you can specify a timeout in the range from 1 through 720 minutes.
You can use longer timeouts or permanent forwarding cache entries in source redundancy scenarios to decrease the time delay inherent in switching from one source to another. With source redundancy, only one source (for example, s1) actively sends traffic at any given time, but the sources can switch. This means that the forwarding state for another source (for example, s2) can time out.
Even though the Routing Engine has the corresponding PIM states set up, when the first (s2,g) packet arrives on each router after a switchover from source s1 to source s2, the router must reinstall the forwarding path (s2,g) if the path has timed out. If many data streams exist, the switchover can take considerable time. Using longer timeouts or permanent cache entries helps reduce the inherent switchover delay.
To configure the multicast forwarding cache timeout for a specified flow map, include the forwarding-cache statement:
-
forwarding-cache {
-
timeout (never | minutes);
- }
You can include this statement at the following hierarchy levels:
For an overview of logical systems and a detailed example of logical system configuration, see the logical systems chapter of the JUNOS Feature Guide.
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Note: The permanent forwarding state must exist on all routers in the path for fast source switchover to function properly. |
For information about configuring multicast flow maps, see Creating a Flow Map.
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