Digisol DG-GS4826S Management Manual page 436

C 16 | Multicast Filtering
HAPTER
Layer 2 IGMP (Snooping and Query)
forwarding is enabled. They are sent upon the occurrence of these
events:
Upon the expiration of a periodic (randomized) timer.
n
As a part of a router's start up procedure.
n
During the restart of a multicast forwarding interface.
n
On receipt of a Solicitation message.
n
Multicast Router Solicitation – Devices send Solicitation messages in
u
order to solicit Advertisement messages from multicast routers. These
messages are used to discover multicast routers on a directly attached
link. Solicitation messages are also sent whenever a multicast
forwarding interface is initialized or re-initialized. Upon receiving a
solicitation on an interface with IP multicast forwarding and MRD
enabled, a router will respond with an Advertisement.
Multicast Router Termination – These messages are sent when a router
u
stops IP multicast routing functions on an interface. Termination
messages are sent by multicast routers when:
Multicast forwarding is disabled on an interface.
n
An interface is administratively disabled.
n
The router is gracefully shut down.
n
Advertisement and Termination messages are sent to the All-Snoopers
multicast address. Solicitation messages are sent to the All-Routers
multicast address.
MRD messages are flooded to all ports in a VLAN where IGMP
N :
OTE
snooping or routing has been enabled. To ensure that older switches which
do not support MRD can also learn the multicast router port, the switch
floods IGMP general query packets, which do not have a null source
address (0.0.0.0), to all ports in the attached VLAN. IGMP packets with a
null source address are only flooded to all ports in the VLAN if the system is
operating in multicast flooding mode, such as when a new VLAN or new
router port is being established, or an spanning tree topology change has
occurred. Otherwise, this kind of packet is only forwarded to known
multicast routing ports.
P
ARAMETERS
These parameters are displayed in the web interface:
VLAN – ID of configured VLANs. (Range: 1-4093)
u
IGMP Snooping Status – When enabled, the switch will monitor
u
network traffic on the indicated VLAN interface to determine which
hosts want to receive multicast traffic. This is referred to as IGMP
Snooping. (Default: Disabled)
When IGMP snooping is enabled globally (see
interface settings for IGMP snooping take precedence.
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page 427), the per VLAN