Source-Based Filtering; Explicit Host Tracking; Mldv2 Snooping Proxy Reporting - Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual

Chapter 26 Configuring MLDv2 Snooping for IPv6 Multicast Traffic

Source-Based Filtering

MLDv2 uses source-based filtering, which enables hosts and routers to specify which multicast sources
should be allowed or blocked for a specific multicast group. Source-based filtering either allows or
blocks traffic based on the following information in MLDv2 messages:
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Because the Layer 2 table is (MAC-group, VLAN) based, with MLDv2 hosts it is preferable to have only
a single multicast source per MAC-group.
Note Source-based filtering is not supported in hardware. The states are maintained only in software and used
for explicit host tracking and statistics collection.

Explicit Host Tracking

MLDv2 supports explicit tracking of membership information on any port. The explicit-tracking
database is used for fast-leave processing, proxy reporting, and statistics collection. When explicit
tracking is enabled on a VLAN, the MLDv2 snooping software processes the MLDv2 report it receives
from a host and builds an explicit-tracking database that contains the following information:
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MLDv2 Snooping Proxy Reporting

Because MLDv2 does not have report suppression, all the hosts send their complete multicast group
membership information to the multicast router in response to queries. The switch snoops these
responses, updates the database and forwards the reports to the multicast router. To prevent the multicast
router from becoming overloaded with reports, MLDv2 snooping does proxy reporting.
Proxy reporting forwards only the first report for a multicast group to the router and suppresses all other
reports for the same multicast group.
Proxy reporting processes solicited and unsolicited reports. Proxy reporting is enabled and cannot be
disabled.
OL-11439-03
Source lists
INCLUDE or EXCLUDE mode
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
Disabling explicit host tracking disables fast-leave processing and proxy reporting.
When explicit tracking is enabled and the switch is in report-suppression mode, the multicast router
might not be able to track all the hosts accessed through a VLAN interface.
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
Understanding How MLDv2 Snooping Works
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