
Configuring IP Multicasting
7-9
Aging a Route
When a router adds or updates a route, it runs configurable aging timers that
control the useful life of the route:
• The route expiration timer is used to time out a route so that it is no longer
used by this router in routing decisions.
• The garbage timer is used to time out a route so that it is no longer propagated
by this router in route updates; once the route expires, it is advertised as
unreachable until it is garbaged or until it receives a route report advertising
reachability.
• The neighbor timer specifies the amount of time the router waits to receive a
report from a neighbor before considering the neighbor.
• The leaf timeout timer determines whether or not a network or tunnel local to
a given interface is considered to be part of the shortest path to a given source
network by any other local network routers.
If the local interface has not received during this time a route report for a
given source network, this network or tunnel and its local interface are
considered not to lie in the shortest path for any local network routers: in other
words, the local network is not part of the shortest path to that specific source
network.
Specifying a Threshold
Threshold values control the scope of datagram delivery. Threshold is the
minimum IP TTL required for a multicast datagram to be forwarded out a given
interface. The interface compares the TTL value of each multicast datagram to be
forwarded with the threshold configured for that interface.
For information on using Site Manager to configure DVMRP timers, see “Editing DVMRP
Global Parameters” on page 7-13.
For information on using Site Manager to specify a threshold value for a DVMRP
interface, see the Threshold parameter on page 7-22. For information on specifying a
threshold value for a tunnel, see the tunnel Threshold parameter on page 7-26.
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