MNS-BB Software User Guide
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hosts connected to switch 1 or switch 2 that belong to the multicast group.
For PC 1 to become a member of the same multicast group without flooding IP multicast traffic
on all ports of switches 1 and 2, IGMP must be configured on both switches 1 and 2, and the port
on Switch 3 that connects to Switch 1 must be unblocked.
12.8 IP Multicast Filters
IP multicast addresses occur in the range from 224.0.0.0 through 239.255.255.255 (which
corresponds to the Ethernet multicast address range of 01005e-000000 through 01005e-7fffff).
Devices such as the LE2425A or LEV2525A having static Traffic/Security filters configured with a
“Multicast” filter type and a “Multicast Address” in this range will continue in effect unless IGMP
learns of a multicast group destination in this range. In that case, IGMP takes over the filtering
function for the multicast destination address(es) for as long as the IGMP group is active. If the IGMP
group subsequently deactivates, the static filter resumes control over traffic to the multicast address
formerly controlled by IGMP.
12.9 Reserved Addresses Excluded from IP Multicast (IGMP) Filtering.
Traffic to IP multicast groups in the IP address range of 224.0.0.0 to 224.0.0.255 will always be
flooded because addresses in this range are “well known” or “reserved” addresses. Thus, if IP
Multicast is enabled and there is an IP multicast group within the reserved address range, traffic to
that group will be flooded instead of filtered by the switch.
12.10 IGMP Support
LE2425A and LEV2525A support IGMP version 1 and version 2. The switch can act either as a
querier or a nonquerier. The querier router periodically sends general query messages to solicit group
membership information. Hosts on the network that are members of a multicast group send report
messages. When a host leaves a group, it sends a leave group message.
The difference between Version 1 and Version 2 is that version 1 does not have a “Leave”
mechanism for the host.
LE2425A and LEV2525A do support pruning when there is a leave message or a time expires on a
port, they prune the multicast group membership on that port.
Note: The LE2425A and LEV2525A support only the default VLAN. It can be enabled within a port
VLAN, tagged VLAN, or no VLAN. It can snoop up to 256 Multicast Groups.
12.11 CLI
12.11.1 Enable/disable IGMP
Syntax: igmp <enable/disable>
Note: By default IGMP is disable.
To enable and disable IGMP in the switch, first go to IGMP context using the command “igmp” or
“configure igmp”.
LE2425A##igmp
LE2425A(igmp)##
LE2425A(igmp)##igmp disable
IGMP is disabled
LE2425A(igmp)##igmp enable
IGMP is enabled
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