3Com 4200G 12-Port, Configuration Manual

Page: 268 / 422

254 C
HAPTER
29: IGMP S
NOOPING
C
ONFIGURATION
In practice, when a user orders a multicast program, an IGMP report message is
generated. When the message arrives at the switch, the switch examines the
multicast filtering ACL configured on the access port to determine if the port can join
the corresponding multicast group or not. If yes, it adds the port to the forward port
list of the multicast group. If not, it drops the IGMP report message and does not
forward the corresponding data stream to the port. In this way, you can control the
multicast streams that users can access.
Configuring to Limit Port
Multicast Group Number
With a limit imposed on the number of multicast groups on a given port, users can no
longer have as many multicast groups as they want, and thereby, control the port
bandwidth effectively.
Configuring Multicast
VLAN
In old multicast mode, when users in different VLANs order the same multicast group,
the multicast stream is copied to each of the VLANs. This mode wastes a lot of
bandwidth.
By configuring a multicast VLAN, adding switch ports to the multicast VLAN and
enabling IGMP Snooping, you can make users in different VLANs share the same
multicast VLAN. This saves bandwidth since multicast streams are transmitted only
within the multicast VLAN, and also guarantees security because the multicast VLAN
is isolated from user VLANs.
Table 225 Configure IGMP Snooping filtering ACL
Operation Command Description
Enter system view system - view —
Enable IGMP Snooping
filter in system view igmp - snooping group - policy acl-number
vlan vlan-id
Optional
acl-number is the
number of a basic ACL;
vlan-id is a VLAN ID. By
default, this function is
not enabled.
Enter Ethernet port
view interface interface-type interface-number
Configure an IGMP
Snooping filtering ACL
on the port igmp - snooping group - policy acl-number
vlan vlan-id
Optional
acl-number is the
number of a basic ACL;
vlan-id is a VLAN ID. By
default, no ACL is
configured on any port.
Table 226 Configure to limit port multicast group number
Operation Command Description
Enter system view system - view -
Enter Ethernet port
view interface interface-type interface-number -
Set a limit to port
multicast group
number on a given
port igmp - snooping group - limit [ vlan vlan - list
| overflow - replace ]
Optional
The number of port
multicast group is not
limited by default