PIM-DM

In a network where IP multicast traffic is transmitted for multimedia applications, traffic is blocked at routed interface (VLAN) boundaries unless a multicast routing protocol is running. PIM is a family of routing protocols that form multicast trees to forward traffic from multicast sources to subnets are using a protocol such as IGMP to request the traffic. PIM relies on the unicast routing tables created by any of several unicast routing protocols to identify the path back to a multicast source, known as reverse path forwarding (RPF.) Based on information provided by the unicast routing tables, PIM sets up a distribution tree for the multicast traffic. The PIM-DM and PIM-SM protocols on the switches enable and control multicast traffic routing.

IGMP provides the multicast traffic link between a host and a multicast router running PIM-DM or PIM-SM. IGMP and either PIM-DM or PIM-SM must be enabled on VLANs whose member ports have directly connected hosts with a valid need to join multicast groups. PIM-DM is used in networks where, at any given time, multicast group members exist in relatively large numbers and are present in most subnets.


	License requirements: In the 3500yl and 5400zl switches, PIM-DM is included with the Premium License.

PIM-DM features

PIM-DM features on switches covered by this guide include:

Routing protocol support

PIM uses whichever unicast routing protocol is running on the routing switch. These can include:

RIP

OSPF

Static routes

Directly connected interfaces

VLAN interface support

The MRT supports up to 128 outbound VLANs at any given time. The sum of all outbound VLANs across all current flows on a router may not exceed 128. (A single flow may span one inbound VLAN and up to 128 outbound VLANs, depending on the VLAN memberships of the hosts actively belonging to the flow.)

Flow capacity

Up to 2048 flows are supported in hardware across a maximum of 128 outbound VLANs. (A flow is composed of an IP source address and an IP multicast group address, regardless of the number of active hosts belonging to the multicast group at any given time.)

IGMP compatibility

PIM-DM is compatible with IGMP (V1 to V3) and is fully interoperable with IGMP for determining multicast flows.

VRRP

PIM-DM is fully interoperable with VRRP to quickly transition multicast routes in the event of a failover.

MIB support

With some exceptions, PIM-DM supports the parts of the multicast routing MIB applicable to PIM-DM operation.

PIM draft specifications

Compatible with PIM-DM draft specifications (V1 and V2.)

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Displaying PIM data and configuration settings	home	PIM-DM operation

Routing protocol support	PIM uses whichever unicast routing protocol is running on the routing switch. These can include: RIP OSPF Static routes Directly connected interfaces
VLAN interface support	The MRT supports up to 128 outbound VLANs at any given time. The sum of all outbound VLANs across all current flows on a router may not exceed 128. (A single flow may span one inbound VLAN and up to 128 outbound VLANs, depending on the VLAN memberships of the hosts actively belonging to the flow.)
Flow capacity	Up to 2048 flows are supported in hardware across a maximum of 128 outbound VLANs. (A flow is composed of an IP source address and an IP multicast group address, regardless of the number of active hosts belonging to the multicast group at any given time.)
IGMP compatibility	PIM-DM is compatible with IGMP (V1 to V3) and is fully interoperable with IGMP for determining multicast flows.
VRRP	PIM-DM is fully interoperable with VRRP to quickly transition multicast routes in the event of a failover.
MIB support	With some exceptions, PIM-DM supports the parts of the multicast routing MIB applicable to PIM-DM operation.
PIM draft specifications	Compatible with PIM-DM draft specifications (V1 and V2.)