Reference Guide

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Multicast Features
Multicast features are supported on the S4820T platform.
NOTE: Multicast is supported on secondary IP addresses on the S4820T platform.
The Dell Networking operating system (FTOS) supports the following multicast protocols:
• PIM Sparse-Mode (PIM-SM)
• Internet Group Management Protocol (IGMP)
• Multicast Source Discovery Protocol (MSDP)
Enabling IP Multicast
Enable IP multicast is supported on the S4820T platform.
Prior to enabling any multicast protocols, you must enable multicast routing.
• Enable multicast routing.
CONFIGURATION mode
ip multicast-routing
Multicast with ECMP
Dell Networking multicast uses equal-cost multi-path (ECMP) routing to load-balance multiple streams across equal
cost links.
When creating the shared-tree protocol independent multicast (PIM) uses routes from all configured routing protocols
to select the best route to the rendezvous point (RP). If there are multiple, equal-cost paths, the PIM selects the route
with the least number of currently running multicast streams. If multiple routes have the same number of streams, PIM
selects the first equal-cost route the route table manager (RTM) returns.
In the following illustration, the receiver joins three groups. The last-hop DR initially has two equal-cost routes to the RP
with no streams, so it non-deterministically selects Route 1 for the Group 1 IGMP Join message. Route 1 then has one
stream associated with it, so the last-hop DR sends the Group 2 Join by Route 2. It then non-deterministically selects
Route 2 for the Group 3 Join because both routes already have one multicast stream.
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