Chapter 20
| Multicast Routing
Configuring PIM for IPv4
– 760 –
Figure 522: Enabling PIM Multicast Routing
Configuring PIM
Interface Settings
Use the Routing Protocol > PIM > Interface page configure the routing protocol’s
functional attributes for each interface.
Command Usage
◆ Most of the attributes on this page are common to both PIM-DM and PIM-SM.
Select Dense or Sparse Mode to display the common attributes, as well as those
applicable to the selected mode.
◆ PIM and IGMP proxy cannot be used at the same time. When an interface is set
to use PIM Dense mode or Sparse mode, IGMP proxy cannot be enabled on any
interface of the device (see “Configuring IGMP Snooping and Query
Parameters” on page 542). Also, when IGMP proxy is enabled on an interface,
PIM cannot be enabled on any interface.
PIM-DM
◆ PIM-DM functions similar to DVMRP by periodically flooding the network with
traffic from any active multicast server. It also uses IGMP to determine the
presence of multicast group members. The main difference, is that it uses the
router’s unicast routing table to determine if the interface through which a
packet is received provides the shortest path back to the source.
◆ Dense-mode interfaces are subject to multicast flooding by default, and are
only removed from the multicast routing table when the router determines
that there are no group members or downstream routers, or when a prune
message is received from a downstream router.
PIM-SM
◆ A PIM-SM interface is used to forward multicast traffic only if a join message is
received from a downstream router or if group members are directly connected
to the interface. When routers want to receive a multicast flow, they
periodically send join messages to the RP, and are subsequently added to the
shared path for the specified flow back up to the RP. If routers want to join the
source path up through the SPT, they periodically send join messages toward
the source. They also send prune messages toward the RP to prune the shared
path once they have connected to the source through the SPT, or if there are no
longer any group members connected to the interface.
To Next Page
Loading...
Need help?
General