Foundry Configuration Guide for the FESX, FSX, and FWSX
19 - 12 © Foundry Networks, Inc. December 2005
The default is 180 seconds.
Modifying Inactivity Timer
The router deletes a forwarding entry if the entry is not used to send multicast packets. The PIM inactivity timer
defines how long a forwarding entry can remain unused before the router deletes it.
To apply a PIM inactivity timer of 90 seconds to all PIM interfaces, enter the following:
FastIron SuperX Router(config)# router pim
FastIron SuperX Router(config-pim-router)# inactivity-timer 90
Syntax: inactivity-timer <10-3600>
The default is 180 seconds.
Selection of Shortest Path Back to Source
By default, when a multicast packet is received on a PIM-capable router interface in a multi-path topology, the
interface checks its IP routing table to determine the shortest path back to the source. If the alternate paths have
the same cost, the first alternate path in the table is picked as the path back to the source. For example, in the
table below, the first four routes have the same cost back to the source. However, 137.80.127.3 will be chosen as
the path to the source since it is the first one on the list. The router rejects traffic from any port other than Port V11
on which 137.80.127.3 resides.
When the Highest IP RPF feature is enabled, the selection of the shortest path back to the source is based on
which Reverse Path Forwarding (RPF) neighbor in the IP routing table has the highest IP address, if the cost of the
routes are the same. For example, in the table above, Gateway 137.80.129.1 will be chosen as the shortest path
to the source because it is the RPF neighbor with the highest IP address.
When choosing the RPF, the router first checks the Multicast Routing Table. If the table is not available, it chooses
an RPF from the IP Routing Table. Multicast route is configured using the ip mroute command.
To enable the Highest IP RPF feature, enter commands such as the following:
FastIron SuperX Router(config)# router pim
FastIron SuperX Router(config-pim-router)# highest-ip-rpf
The command immediately enables the Highest IP RPF feature; there is no need to reboot the device.
Syntax: [no] highest-ip-rpf
Entering the no version of the command disables the feature; the shortest path back to the source will be based
on the first entry in the IP routing table. If some PIM traffic paths were selected based on the highest IP RPF, these
paths are changed immediately to use the first RPF in the routing table.
Total number of IP routes: 19
B:BGP D:Connected R:RIP S:Static O:OSPF *:Candidate default
Destination NetMask Gateway Port Cost
Type
..
9 172.17.41.4 255.255.255.252*137.80.127.3 v11 2
O
172.17.41.4 255.255.255.252 137.80.126.3 v10 2
O
172.17.41.4 255.255.255.252 137.80.129.1 v13 2
O
172.17.41.4 255.255.255.252 137.80.128.3 v12 2
O
10 172.17.41.8 255.255.255.252 0.0.0.0 1/2 1
D
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