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Chapter 8

Security, Timers, and Traffic Engineering in IP Multicast Networks

Adjusting Timers for IP Multicast

Adjusting Timers for IP Multicast

10.5.10.1

Vlan10

v2/Sparse

0

1

10.5.10.1

10.0.0.37

GigabitEthernet0/1

v2/Sparse

1

1

10.0.0.38

10.0.0.41

GigabitEthernet0/2

v2/Sparse

1

1

10.0.0.42

Announce Interval

The ip pim send-rp-announce command has an interval option. Adjusting the interval allows for faster RP failover when using Auto-RP. The default interval is 60 seconds and the holdtime is 3 times the interval. So the default failover time is 3 minutes. The lower the interval, the faster the failover time. Decreasing the interval will increase Auto-RP traffic but not enough to cause any kind of a performance impact. If the default is to be changed, use the recommended values of 3 to 5 seconds.

Two timers can be adjusted to facilitate faster failover of multicast streams. The timers control the: Query Interval Announce Interval

DR

Query Interval

The ip pim query-interval command configures the frequency of PIM Router-Query messages. Router Query messages are used to elect a PIM DR. The default value is 30 seconds. If the default value is changed, the recommended interval is 1 second.

To verify the interval for each interface, issue the show ip pim interface command, as shown below.

Nbr Query Count Intvl

3550-svrL-dist#show ip pim interface

Address

Interface

Version/Mode

Traffic Engineering

Traffic engineering adds a great deal of control to IP multicast deployment and operation. It also adds complexity. One option for controlling IP multicast is through the use of scoped boundaries.

The ip multicast boundary command configures an administratively scoped boundary on an interface and permits or denies multicast group addresses found in the access-list. No multicast packets will be allowed to flow across the boundary from either direction. This allows reuse of the same multicast group address in different administrative domains.

If the RPF interface for a multicast route has a multicast boundary configured for that group, its outgoing interfaces will not be populated with multicast forwarding state. Join messages received on other interfaces will be ignored as long as the boundary remains on the RPF interface. If the RPF interface changes and the boundary no longer applies to the new RPF interface, join latency will be introduced because of the delay in populating outgoing interfaces.

The boundary controls traffic based on the permit/deny configuration of the ACL associated with the boundary command.

Cisco AVVID Network Infrastructure IP Multicast Design

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