Tcn Multicast Flooding - SMC Networks 7824M/VSW - annexe 1 Manual

CLI
9.2.3.8
366

TCN Multicast Flooding

When a network topology change occurs, the protocols for a link layer topology – such as
spanning tree protocol (STP), Ethernet ring protection (ERP), etc – notify switches in the
topology using a topology change notification (TCN).
When TCN is received, the switch where an IGMP snooping is running will flood multicast
traffic to all ports in a VLAN, since a network topology change in a VLAN may invalidate
previously learned IGMP snooping information. However, this flooding behavior is not de-
sirable if the switch has many ports that are subscribed to different groups. The traffic
could exceed the capacity of the link between the switch and the end host, resulting in
packet loss. Thus, a period of multicast flooding needs to be controlled to solve such a
problem.
Enabling TCN Multicast Flooding
To enable the switch to flood multicast traffic when TCN is received, use the following
command.
Command
ip igmp snooping tcn flood
ip igmp snooping tcn
VLANS flood
To disable the switch to flood multicast traffic when TCN is received, use the following
command.
Command
no ip igmp snooping tcn flood
no ip igmp snooping tcn vlan
VLANS flood
TCN Flooding Suppression
When TCN is received, the switch where an IGMP snooping is running will flood multicast
traffic to all ports until receiving two general queries, or during two general query intervals
by default. You can also configure the switch to stop multicast flooding according to a
specified query count or query interval.
To specify a query count to stop multicast flooding, use the following command.
Command
ip igmp snooping tcn flood
query count <1-10>
no ip igmp snooping tcn flood
query count
Mode
Enables the switch to flood multicast traffic when TCN
is received.
Global
Enables the switch to flood multicast traffic on a VLAN
vlan
when TCN is received.
VLANS: VLAN ID (1-4094)
Mode
Disables the switch to flood multicast traffic when TCN
Global
is received
Mode
Specifies a query count to stop multicast flooding.
1-10: query count value (default: 2)
Global
Deletes a specified query count to stop multicast flood-
ing.
Management Guide
TigerAccess™ EE
Description
Description
Description
SMC7824M/VSW