Brocade TurboIron 24X Series Configuration Guide - Manual (Page 840)

806 Brocade TurboIron 24X Series Configuration Guide
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PIM Sparse
Failover time in a multi-path topology
When a port in a multi-path topology fails, and the failed port is the input port of the downstream
router, a new path is re-established within a few seconds, depending on the routing protocol being
used.
No configuration is required for this feature.
Modifying the TTL
The TTL defines the minimum value required in a packet for it to be forwarded out of the interface.
For example, if the TTL for an interface is set at 10, it means that only those packets with a TTL
value of 10 or more will be forwarded. Likewise, if an interface is configured with a TTL Threshold
value of 1, all packets received on that interface will be forwarded. Possible TTL values are 1 to 31.
The default TTL value is 1.
Configuration notes
• If the TTL for an interface is greater than 1, PIM packets received on the interface are always
forwarded in software because each packet TTL must be examined. Therefore, Brocade does
not recommend modifying the TTL under normal operating conditions.
• Multicast packets with a TTL value of 1 are switched within the same VLAN. These packets
cannot be routed between different VLANs.
Configuration syntax
To configure a TTL of 24, enter the following.
TurboIron(config-if-24)#ip pim ttl 24
Syntax: ip pim ttl <1-31>
Dropping PIM traffic in hardware
Unwanted PIM Dense or PIM Sparse multicast traffic can be dropped in hardware on Layer 3
Switches. Refer to
“Passive multicast route insertion” on page 830.
PIM Sparse
Devices support Protocol Independent Multicast (PIM) Sparse version 2. PIM Sparse provides
multicasting that is especially suitable for widely distributed multicast environments. The Brocade
implementation is based on RFC 2362.
In a PIM Sparse network, a PIM Sparse router that is connected to a host that wants to receive
information for a multicast group must explicitly send a join request on behalf of the receiver (host).
PIM Sparse routers are organized into domains. A PIM Sparse domain is a contiguous set of routers
that all implement PIM and are configured to operate within a common boundary.
Figure 106
shows a simple example of a PIM Sparse domain. This example shows three Layer 3 Switches
configured as PIM Sparse routers. The configuration is described in detail following the figure.
FIGURE 106 Example of a PIM Sparse domain