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Configuring IP Multicast Routing
Monitoring and Maintaining IP Multicast Routing Configuration Task List
IPC-445
Cisco IOS IP Configuration Guide
Verifying the Load Splitting
Load splitting works for both fast switching and process switching, but splitting the traffic among the
physical interfaces is performed differently for each case. Fast switching occurs if both the incoming and
outgoing interfaces are configured with the ip mroute-cache interface configuration command. IP
multicast fast switching is enabled by default. Note the following properties of load splitting:
• With process switching, load splitting occurs on a per-packet basis by round robin on the equal-cost
links. To verify that load splitting is working, look at the interface statistics using the show
interfaces accounting EXEC command, and verify that the packet count is about equal for the
underlying interfaces that provide the equal-cost paths.
• With fast switching, load splitting occurs on a per-flow basis. A flow is a set of traffic with the same
source and destination. Once the cache is populated for the (S, G) pair, that flow is pinned to the
physical interface assigned on the cache (the outgoing interface used by the first packet of the flow).
If the cached interface goes down, the cache entry for the (S, G) pair is torn down and the flow is
automatically switched to a different physical interface.
In the case of fast switching, you can verify that load splitting is occurring by viewing the multicast
fast-switched cache by using the show ip mcache EXEC command. The flows should be split among the
underlying interfaces, as shown in the following example:
Router# show ip mcache
IP Multicast Fast-Switching Cache
(100.1.1.6/32, 224.1.1.1), Ethernet0, Last used: 00:00:00
Tunnel0 MAC Header: 0F000800 (Serial1)
(100.1.1.6/32, 224.1.1.2), Ethernet0, Last used: 00:00:00
Tunnel0 MAC Header: 0F000800 (Serial1)
(100.1.1.5/32, 224.1.1.3), Ethernet0, Last used: 00:00:00
Tunnel0 MAC Header: 0F000800 (Serial0)
(100.1.1.5/32, 224.1.1.4), Ethernet0, Last used: 00:00:00
Tunnel0 MAC Header: 0F000800 (Serial0)
For an example of load splitting IP multicast traffic across equal-cost paths, see the section “Load
Splitting IP Multicast Traffic Across Equal-Cost Paths Example” later in this chapter.
Monitoring and Maintaining IP Multicast Routing Configuration
Task List
To monitor and maintain IP multicast routing, perform the optional tasks described in the following
sections.
• Clearing Caches, Tables, and Databases (Optional)
• Displaying System and Network Statistics (Optional)
• Using IP Multicast Heartbeat (Optional)
Note For information about Multicast Routing Monitor (MRM) and commands that monitor IP multicast
information, see the chapter “Using IP Multicast Tools.”