30-7
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 30 Configuring IGMP Snooping for IPv4 Multicast Traffic
Default IGMP Snooping Configuration
Note • Source-based filtering for IGMP version 3 reports is not supported in hardware. The states are
maintained only in software and used for explicit host tracking and statistics collection. The
source-only entries are deleted every 5 minutes and relearned to ensure that they are still valid.
• Turning off explicit host tracking disables fast-leave processing and proxy reporting.
Explicit Host Tracking
IGMPv3 supports explicit tracking of membership information on any port. The explicit-tracking
database is used for fast-leave processing for IGMPv3 hosts, proxy reporting, and statistics collection.
When explicit tracking is enabled on a VLAN, the IGMP snooping software processes the IGMPv3
report it receives from a host and builds an explicit-tracking database that contains the following
information:
• The port connected to the host
• The channels reported by the host
• The filter mode for each group reported by the host
• The list of sources for each group reported by the hosts
• The router filter mode of each group
• For each group, the list of hosts requesting the source
Note • Turning off explicit host tracking disables fast-leave processing and proxy reporting.
• When explicit tracking is enabled and the router is working in proxy-reporting mode, the router may
not be able to track all the hosts behind a VLAN interface.
Default IGMP Snooping Configuration
Table 30-3 shows the default IGMP snooping configuration.
Table 30-3 IGMP Snooping Default Configuration
Feature Default Values
IGMP snooping querier Disabled
IGMP snooping Enabled
Multicast routers None configured
IGMPv3 proxy reporting Enabled
IGMP snooping router learning
method
Learned automatically through PIM or IGMP packets
Fast-Leave Processing Disabled
IGMPv3 Explicit Host Tracking Enabled
IGMPv3 SSM Safe Reporting Disabled; deprecated in Release 12.2(18)SXE and later releases
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