Igmp Snooping; Static Igmp; Igmp Snooping Filters - Extreme Networks ExtremeWare 7.2e Installation And User Manual

IP Multicast Routing

IGMP Snooping

IGMP snooping is a layer 2 function of the switch. It does not require multicast routing to be enabled. In
IGMP snooping, the layer 2 switch keeps track of IGMP requests, and only forwards multicast traffic to
the part of the local network that requires it. IGMP snooping optimizes the usage of network
bandwidth, and prevents multicast traffic from being flooded to parts of the local network that do not
need it. The switch does not reduce any IP multicast traffic in the local multicast domain (224.0.0.x).
IGMP snooping is enabled by default on the switch. If IGMP snooping is disabled, all IGMP and IP
multicast traffic floods within a given VLAN. IGMP snooping expects at least one device on every
VLAN to periodically generate IGMP query messages. The static IGMP snooping entries do not require
periodic query. An optional optimization for IGMP snooping is the strict recognition of multicast routers
only if the remote devices have joined the PIM (244.0.0.13) multicast groups.
When a port sends an IGMP leave message, the switch removes the IGMP snooping entry after 1000
milli-seconds (the leave time is configurable, ranging from 0 to 10000 ms). The switch sends a query to
determine which ports want to remain in the multicast group. If other members of the VLAN want to
remain in the multicast group, the router ignores the leave message, but the port that requests removal
is removed from the IGMP snooping table.
If the last port within a VLAN sends an IGMP leave message, then the router will not receive any
responses to the query, and the router immediately will remove the VLAN from the multicast group.

Static IGMP

In order to receive multicast traffic, a host needs to explicitly join a multicast group by sending an
IGMP request, then the traffic is forwarded to that host. There are situations where you would like
multicast traffic to be forwarded to a port where a multicast enabled host is not available (for example,
testing multicast configurations). Static IGMP emulates a host or router attached to a switch port, so
that multicast traffic will be forwarded to that port. Emulate a host to forward a particular multicast
group to a port; emulate a router to forward all multicast groups to a port. Use the following command
to emulate a host on a port:
configure igmp snooping vlan <vlan name> ports <portlist> add static group <ip
address>
Use the following command to emulate a multicast router on a port:
configure igmp snooping vlan <vlan name> ports <portlist> add static router
To remove these entries, use the corresponding command:
configure igmp snooping vlan <vlan name> ports <portlist> delete static group [<ip
address> | all]
configure igmp snooping vlan <vlan name> ports <portlist> delete static router
To display the IGMP snooping static groups, use the following command:
show igmp snooping {vlan <vlan name>} static group

IGMP Snooping Filters

IGMP snooping filters allow you to configure an access profile on a port to allow or deny IGMP report
and leave packets coming into the port. For details on creating access profiles, see the section, "Routing
Access Profiles" on page 160. For the access profiles used as IGMP snooping filters, all the profile entries
252 ExtremeWare 7.2e Installation and User Guide