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DES-7200 Configuration Guide Chapter 9 MLD Snooping Configuration
9-3
class ranges are not within the application area of SVGL, and all multicast stream
will be discarded.
The two modes of IVGL and SVGL may coexist, you may allocate with MLD
Profile a number of multicast addresses ranges to SVGL, within such ranges the
listener ports of the multicast forwarding-table may transmit across VLAN.
However, the listener ports of the multicast forwarding-tables within other
multicast address ranges must belong to the same VLAN.
9.1.2.4 Understanding source port check
Some of the layer 2 multicast equipments newly launched by DES-7200 provide
support to check MLD Snooping source port, thus enhancing network security.
MLD Snooping source port check means strict limitation of porting of MLD
multicast stream. When MLD Snooping source port check is disabled, multicast
stream incoming from any port is legal and can be transmitted to registered
listener port(s) according to MLD Snooping forwarding-table by layer 2 multicast
equipment. When MLD Snooping source port check is enabled, only multicast
stream incoming from router port is legal and can be transmitted to registered
port(s) by layer 2 multicast equipment; while multicast stream incoming from
non-router port is considered illegal and will be discarded.
9.1.3 Working Principle of MLD Snooping
The switch that runs MLD Snooping processes different MLD messages in the
following ways:
1. MLD QUERY
Layer 3 multicast equipments regularly send group-general query message to all
hosts and routers (address: FF 02::1) within local network segment to find out
which listeners of IPv 6 multicast group exist in this local network segment. A
switch transmits MLD group-general query message being received to all other
ports except receive port within VLAN and process the receive port in the
following ways:
If the port is already included in the list of router ports, its aging timer should be
reset.
If the port is not included in the list of router ports, it should be added to the list of
router ports and its aging timer should be enabled.
Whenever receiving MLD group-general query message, layer 2 multicast
equipment will update respective aging timers of all listener ports and demote the
timer to configured MLD query-max-response-time.
When the timer value is
reduced to "0", it is considered that there is no longer any listener of the port
receiving multicast stream. Layer 2 multicast equipment will delete the port from
MLD Snooping forwarding-table.
Whenever receiving MLD group-specific query message, layer 2 multicast
equipment will update aging timers of all listener ports in the specific group, and
demote the timer to configured MLD query-max-response-time.
When the timer
value is reduced to "0", it is considered that there is no longer any listener of the
port receiving multicast stream. Layer 2 multicast equipment will delete the port
from MLD Snooping forwarding-table.
When receiving MLD group-specific source query message, the aforesaid two
kinds of timers will not be updated.
2. MLD REPORT