Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 397

Source-Based Filtering, Explicit Host Tracking, MLDv2 Snooping Proxy Reporting

Page 397 highlights

Chapter 26 Configuring MLDv2 Snooping for IPv6 Multicast Traffic Understanding How MLDv2 Snooping Works 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: • Source lists • INCLUDE or EXCLUDE mode 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: • 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 • 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. 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 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY 26-3

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26-3
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
OL-11439-03
Chapter 26
Configuring MLDv2 Snooping for IPv6 Multicast Traffic
Understanding How MLDv2 Snooping Works
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:
Source lists
INCLUDE or EXCLUDE mode
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:
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
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.
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
.