KB.15.15

NOTE: When you initially enable PIM-DM, it is recommended that you leave the PIM-DM

configuration parameters at their default settings. From the default, you can assess performance

and make configuration changes when needed.

About configuring PIM-DM

PIM-DM requires configuration on both the global level and on the VLAN (interface) level. The

recommended configuration order is:

1. Enable IGMP on all VLANs where hosts may join a multicast group.

2. Enable the following at the global level:

• IP routing

• IP multicast routing

• Router PIM and any non-default, global PIM settings you want to apply

• Router RIP, Router OSPF, and/or a static route

3. If you selected RIP or OSPF in step 2: enable the same option on each VLAN where you want

multicast routing to operate.

4. Enable the following in each VLAN context where you want multicast routing to operate:

• IP RIP or IP OSPF

• IP PIM

• Any non-default, VLAN-level IP PIM settings you want to apply

Operating notes

PIM-DM operating rules

• The routing switch supports 2048 multicast flows in hardware. See,“Flow capacity” (page 59).

• The multicast routing table (MRT) that PIM-DM creates allows up to 128 outbound VLANs at

any given time. PIM-DM supports multicast routing across 128 VLANs.

• The routing switch allows one instance of PIM per VLAN. For networks using multinetted VLANs,

all routers on the intended VLAN must have at least one common subnet if you intend on

routing multicast packets. The routing switch provides a command for specifying which IP

address PIM will use on each VLAN.

PIM routers without state-refresh messaging capability

A PIM router without a state-refresh messaging capability learns of currently active flows in a

multicast network through periodic flood and prune cycles on the path back to the source. The

switches covered in this guide sense downstream multicast routers that do not have the state-refresh

capability and will periodically flood active multicast groups to these devices. This periodic flooding

is not necessary if all downstream multicast routers are switches covered in this guide. (The HP

routing switch Series 9300 and the routers offered by some other vendors do not offer the

state-refresh capability.)

Flow capacity

The routing switch provides an ample multicast environment, supporting 2048 multicast flows in

hardware across a maximum of 64 VLANs. (A flow comprises a unicast source address and a

multicast group address, regardless of the number of active hosts belonging to the multicast group

at any given time.)

About configuring PIM-DM 59