Igmp Snoop And Proxy; Multicast Vlan Registration (Mvr) - Avaya 8800 Planning And Engineering, Network Design

Multicast network design
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Multicast VLAN Registration (MVR)

• IGMP Layer 2 querier

IGMP snoop and proxy

On a Layer 2 VLAN, if at least one host on the VLAN specifies that it is a member of a multicast
group, by default, the Avaya Ethernet Routing Switch 8800/8600 forwards to that VLAN all
datagrams bearing the multicast address of that group. All ports on the VLAN receive the traffic for
that group.
With IGMP snoop enabled on a VLAN, the Avaya Ethernet Routing Switch 8800/8600 forwards the
multicast group data to only those ports that are members of the multicast group.
The switch identifies multicast group members by listening to IGMP packets (IGMP reports, leaves,
and queries) from each port. Using the information gathered from the reports, the switch builds a list
of group members. After the group members are identified, the switch blocks the IP Multicast stream
from exiting any port that does not connect to a group member, conserving bandwidth.
With IGMP snoop enabled, the switch can receive multiple reports for the same multicast group.
Rather than forward each report upstream, the Ethernet Routing Switch 8800/8600 can consolidate
these multiple reports using the IGMP proxy feature. With IGMP proxy enabled, if the switch
receives multiple reports for the same multicast group, it does not transmit each report to the
upstream multicast router. Instead, the switch forwards the first report to the querier and suppresses
the rest. If new information emerges, for example if the switch adds another multicast group or
receives a query since the last report is transmitted upstream, then the switch forwards a new report
to the multicast router ports.
For more information about IGMP snoop and proxy, see Avaya Ethernet Routing Switch 8800/8600
Configuration — IP Multicast Routing Protocols (NN46205-501).
Multicast VLAN Registration (MVR)
On Layer 2 VLANs, the Avaya Ethernet Routing Switch 8800/8600 uses IGMP Snoop to listen for
report, leave and query packets, and then creates or deletes multicast groups for receiver ports to
receive multicast data streams. In IGMP Snoop, all the ports, including receiver and source ports,
are members of the same VLAN. When users in different VLANs join the same group, the multicast
router replicates one stream into multiple streams that are sent to these VLANs. Multiple streams
waste bandwidth and decrease the performance of the multicast router.
The Multicast VLAN Registration (MVR) Protocol solves this problem. With MVR, the receiver ports
remain in the IGMP Snoop VLAN, but one VLAN is designated as the MVR VLAN. Each VRF on the
Ethernet Routing Switch 8800/8600 supports only one MVR VLAN.
The MVR VLAN has a source port, which connects to the multicast router. After you bind several
IGMP Snoop VLANs to the MVR VLAN, and a multicast data packet arrives from the source port,
the switch replicates this packet and forwards it to all the IGMP Snoop VLANs that are bound to the
MVR VLAN.
June 2016
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on page 189
Planning and Engineering — Network Design
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