Multicast Filtering
15-2
15
Layer 2 IGMP
(Snooping and Query)
IGMP Snooping and Query – If multicast routing is not supported on other switches
in your network, you can use IGMP Snooping and IGMP Query (page 15-3) to
monitor IGMP service requests passing between multicast clients and servers, and
dynamically configure the switch ports which need to forward multicast traffic.
When using IGMPv3 snooping, service requests from IGMP Version 1, 2 or 3 hosts
are all forwarded to the upstream router as IGMPv3 reports. The primary
enhancement provided by IGMPv3 snooping is in keeping track of information about
the specific multicast sources which downstream IGMPv3 hosts have requested or
refused. The switch maintains information about both multicast groups and
channels, where a group indicates a multicast flow for which the hosts have not
requested a specific source (the only option for IGMPv1 and v2 hosts unless
statically configured on the switch), and a channel indicates a flow for which the
hosts have requested service from a specific source.
Only IGMPv3 hosts can request service from a specific multicast source. When
downstream hosts request service from a specific source for a multicast service,
these sources are all placed in the Include list, and traffic is forwarded to the hosts
from each of these sources. IGMPv3 hosts may also request that service be
forwarded from all sources except for those specified. In this case, traffic is filtered
from sources in the Exclude list, and forwarded from all other available sources.
Notes: 1.
When the switch is configured to use IGMPv3 snooping, the snooping
version may be downgraded to version 2 or version 1, depending on the
version of the IGMP query packets detected on each VLAN.
2.
IGMP snooping will not function unless a multicast router port is enabled on
the switch. This can be accomplished in one of two ways. A static router port
can be manually configured (see “Specifying Static Interfaces for a Multicast
Router” on page 15-7). Using this method, the router port is never timed out,
and will continue to function until explicitly removed. The other method relies
on the switch to dynamically create multicast routing ports whenever
multicast routing protocol packets or IGMP query packets are detected on a
port.
3.
A maximum of up to 255 multicast entries can be maintained for IGMP
snooping, and 255 entries for Multicast Routing, when both of these features
are enabled. If the table’s capacity is exceeded, the IGMPv3 snooping will
not support multicast source filtering, but will forward multicast traffic from all
relevant sources to the requesting hosts.
Static IGMP Router Interface – If IGMP snooping cannot locate the IGMP querier,
you can manually designate a known IGMP querier (i.e., a multicast router/switch)
connected over the network to an interface on your switch (page 15-7). This
interface will then join all the current multicast groups supported by the attached
router/switch to ensure that multicast traffic is passed to all appropriate interfaces
within the switch.
Summary of Contents for 8926EM
Page 6: ...ii ...
Page 34: ...Getting Started ...
Page 44: ...Introduction 1 10 1 ...
Page 62: ...Initial Configuration 2 18 2 ...
Page 64: ...Switch Management ...
Page 76: ...Configuring the Switch 3 12 3 ...
Page 118: ...Basic Management Tasks 4 42 4 ...
Page 164: ...User Authentication 6 28 6 ...
Page 176: ...Access Control Lists 7 12 7 ...
Page 284: ...Quality of Service 14 8 14 ...
Page 294: ...Multicast Filtering 15 10 15 ...
Page 300: ...Domain Name Service 16 6 16 ...
Page 310: ...Dynamic Host Configuration Protocol 17 10 17 ...
Page 320: ...Configuring Router Redundancy 18 10 18 ...
Page 344: ...IP Routing 19 24 19 ...
Page 356: ...Unicast Routing 20 12 20 Web Click Routing Protocol RIP Statistics Figure 20 5 RIP Statistics ...
Page 386: ...Unicast Routing 20 42 20 ...
Page 388: ...Command Line Interface ...
Page 400: ...Overview of the Command Line Interface 21 12 21 ...
Page 466: ...SNMP Commands 24 16 24 ...
Page 520: ...Access Control List Commands 26 18 26 ...
Page 546: ...Rate Limit Commands 30 2 30 ...
Page 612: ...VLAN Commands 34 24 34 ...
Page 626: ...Class of Service Commands 35 14 35 ...
Page 670: ...DHCP Commands 39 16 39 ...
Page 716: ...IP Interface Commands 41 36 41 ...
Page 768: ...IP Routing Commands 42 52 42 ...
Page 770: ...Appendices ...
Page 791: ......