Igmpv3; Igmp Snooping Querier; Static Multicast Mac Address - Cisco Nexus 7000 Series Configuration Manual

Configuring IGMP Snooping

IGMPv3

The IGMPv3 snooping implementation on Cisco NX-OS supports full IGMPv3 snooping, which provides
constrained flooding based on the (S, G) information in the IGMPv3 reports. This source-based filtering
enables the device to constrain multicast traffic to a set of ports based on the source that sends traffic to the
multicast group.
By default, the software tracks hosts on each VLAN port. The explicit tracking feature provides a fast leave
mechanism. Because every IGMPv3 host sends membership reports, report suppression limits the amount of
traffic that the device sends to other multicast-capable routers. When report suppression is enabled, and no
IGMPv1 or IGMPv2 hosts requested the same group, the software provides proxy reporting. The proxy feature
builds the group state from membership reports from the downstream hosts and generates membership reports
in response to queries from upstream queriers.
Even though the IGMPv3 membership reports provide a full accounting of group members on a LAN segment,
when the last host leaves, the software sends a membership query. You can configure the parameter last
member query interval. If no host responds before the timeout, the software removes the group state.

IGMP Snooping Querier

When PIM is not enabled on an interface because the multicast traffic does not need to be routed, you must
configure an IGMP snooping querier to send membership queries. You define the querier in a VLAN that
contains multicast sources and receivers but no other active querier.
The querier can be configured to use any IP address in the VLAN.
As a best practice, a unique IP address, one that is not already used by the switch interface or the HSRP VIP,
should be configured so as to easily reference the querier. In a vPC configuration too, the querier IP should
be unique on the vPC primary and secondary.
Note
The IP address for the querier should not be a broadcast IP, multicast IP, or 0(0.0.0.0).
When an IGMP snooping querier is enabled, it sends out periodic IGMP queries that trigger IGMP report
messages from hosts that want to receive IP multicast traffic. IGMP snooping listens to these IGMP reports
to establish appropriate forwarding.
The IGMP snooping querier performs querier election as described in RFC 2236. A querier election occurs
in the following configurations:
• When there are multiple switch queriers configured with the same subnet on the same VLAN on different
• When the configured switch querier is in the same subnet as with other Layer 3 SVI queriers.

Static Multicast MAC Address

Beginning with the Cisco Release 5.2(1) for the Nexus 7000 Series devices, you configure an outgoing interface
statically for a multicast MAC address. Also, you can configure the IGMP snooping to use a MAC-based
lookup mode.
switches.
Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide
IGMPv3
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