Design Reference

that must be reached by all PIM-enabled switches with receivers in a network, placing the RP on a
split-subnet can impact the whole multicast traffic flow. Traffic can be affected even for receivers
and senders that are not part of the split-subnet.
Protocol Independent Multicast-Sparse Mode guidelines
Protocol Independent Multicast-Sparse Mode (PIM-SM) uses an underlying unicast routing
information base to perform multicast routing. PIM-SM builds unidirectional shared trees rooted at a
RP router for each group and can also create shortest-path trees for each source.
PIM-SM and PIM-SSM scalability
Values for VSP 4000 active and passive interface scaling can be found in Release Notes for VSP
Operating System Software, NN47227-401.
The current release does not support virtualized PIM. PIM is supported in the Global Routing Table
only.
Interfaces that run PIM must also use a unicast routing protocol (PIM uses the unicast routing table),
which puts stringent requirements on the system. With a high number of interfaces, take special
care to reduce the load on the system.
Use few active IP routed interfaces. You can use IP forwarding without a routing protocol enabled
on the interfaces, and enable only one or two with a routing protocol. You can configure proper
routing by using IP routing policies to announce and accept routes on the switch. Use PIM passive
interfaces on the majority of interfaces.
Important:
Refer to Release Notes for VSP Operating System Software, NN47227-401 for maximum
values for total PIM interfaces and active interfaces. If you configure the maximum amount of
active interfaces, all remaining interfaces must be passive.
When you use PIM-SM, the number of routes can scale up to the unicast route limit because PIM
uses the unicast routing table to make forwarding decisions. For higher route scaling, Avaya
recommends that you use OSPF rather than Routing Information Protocol (RIP).
As a general rule, a well-designed network does not have many routes in the routing table. For PIM
to work properly, ensure that all subnets configured with PIM are reachable and that PIM uses the
information in the unicast routing table. For the RPF check, to correctly reach the source of any
multicast traffic, PIM requires the unicast routing table. For more information, see
PIM network with
non-PIM interfaces on page 143.
PIM general requirements
Avaya recommends that you design simple PIM networks where VLANs do not span several
switches.
PIM relies on unicast routing protocols to perform its multicast forwarding. As a result, include in
your PIM network design, a unicast design where the unicast routing table has a route to every
source and receiver of multicast traffic, as well as a route to the RP router and Bootstrap router
(BSR) in the network. Ensure that the path between a sender and receiver contains PIM-enabled
interfaces. Receiver subnets are not always required in the routing table.
Protocol Independent Multicast-Sparse Mode guidelines
June 2015 Network Design Reference for Avaya VSP 4000 Series 133
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