VRRP:
PIM-SM is fully interoperable with VRRP to quickly transition multicast routes in the event of a failover.
MIB support on the switches covered in this guide:
PIM-SM supports the Protocol Independent Multicast MIB for IPv4 (RFC 2934.)
With some exceptions, PIM-SM supports the parts of the multicast routing MIB (RFC 2932) applicable to PIM-
SM operation.
PIM draft specifications:
Compatible with PIM-SM specification ( RFC 4061.)
BSR implementation:
Complies with RFC 5059 (scope zones are not supported.)
Maximum number of routes:
For the 2930F switch, the maximum number of routes is limited to 200.
PIM-SM operation and router types
Unlike PIM-DM, PIM-SM assumes that most hosts do not want to receive multicast traffic, and uses a non-
flooding multicast model to direct traffic for a particular multicast group from the source to the VLAN(s) where
there are multicast receivers that have joined the group. As a result, this model sends traffic only to the routers
that specifically request it.
PIM-SM operation
In a given PIM-SM domain, routers identified as DRs, RPs, and a BSR participate in delivering multicast traffic to
the IP multicast receivers that request it. This approach avoids the flooding method of distributing multicast traffic
(employed by PIM-DM) and is best suited for lower bandwidth situations.
The software supports the following operation to enable multicast traffic delivery within a PIM-SM domain:
• From a pool of eligible DR candidates in each VLAN, one DR is elected for each VLAN interface having at
least one PIM-SM router. In a multinetted domain, this DR supports multicast traffic from a source on any
subnet in the VLAN.
• From a pool of eligible BSR candidates in the domain, one BSR is elected for the entire domain.
• From a pool of eligible C-RPs, one is elected to support each multicast group or range of groups allowed in the
domain, excluding any group supported only by static RPs. The multicast groups allowed in the domain are
determined by the aggregation of the groups allowed by the individually configured RPs and any static RPs.
(Note that RP-Cs and static RP’s can be configured with overlapping support for a given set of multicast
groups.)
Rendezvous-point tree (RPT)
When a DR in a VLAN receives traffic for a particular multicast group from a source on that VLAN, the DR
encapsulates the traffic and forwards it to the RP elected to support that multicast group. The RP decapsulates
the traffic and forwards it on toward the multicast receiver(s) requesting that group. This forms an RPT extending
from the DR through any intermediate PIM-SM routers leading to the PIM-SM edge router(s) for the multicast
receiver(s) requesting the traffic. (If the RP has no current join requests for the group, the traffic is dropped at the
RP.)
Figure 20: Example PIM-SM domain with RPT active to support a host joining a multicast group
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Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
Switch 16.08
