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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter34 Configuring IP Multicast Routi ng Configuring IP Multicast Routing
•If you have non-Cisco PIMv2 routers that need to interoperate with Cisco PIMv1 routers and
multilayer switches, both Auto-RP and a BSR are required. We recommend that a Cisco PIMv2
device be both the Auto-RP mapping agent and the BSR. For more information, see the “Using
Auto-RP and a BSR” section on page 34-20.
Configuring Basic Multicast Routing
You must enable IP multicast routing and configure the PIM version and the PIM mode. Then the
software can forward multicast packets, and the switch can populate its multicast routing table.
Note To enable IP multicast routing, the switch must be running the metro IP access image.
You can configure an interface to be in PIM dense mode, sparse mode, or sparse-dense mode. The switch
populates its multicast routing table and forwards multicast packets it receives from its directly
connected LANs according to the mode setting. You must enable PIM in one of these modes for an
interface to perform IP multicast routing. Enabling PIM on an interface also ena bles IGMP operat ion on
that interface.
In populating the multicast routing table, dense-mode int erfac e s are always adde d to t he t abl e.
Sparse-mode interfaces are added to the table on l y wh en pe riod ic jo in m es s ag es ar e rec eived fro m
downstream devices or when there is a directly connected member on the interface. When forwarding
from a LAN, sparse-mode operation occurs if there is an RP known fo r the group. If so, the packets are
encapsulated and sent toward the RP. When no RP is known, the packet is flooded in a dense-mode
fashion. If the multicast traffic from a specific source is sufficient, the receiver’s first-hop router might
send join messages toward the source to build a source-based distribution tree.
By default, multicast routing is disabled, and there is no default mode setting. This procedure is required.
Beginning in privileged EXEC mode, follow these steps to enable IP multicasting, to configure a PIM
version, and to configure a PIM mode. This procedure is req ui red.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 ip multicast-routing distributed Enable IP multicast distributed switching.
Step3 interface interface-id Specify the Layer 3 interface on which you want to enable multicast
routing, and enter interface configuration mode.
The specified interface must be one of the following:
•A routed port: a physical port that has been configured as a Layer 3
port by entering the no switchport interface configuration
command.
•An SVI: a VLAN interface created by using the interface vlan
vlan-id global configuration command.
These interfaces must have IP addresses assigned to them. For more
information, see the “Configuring Layer 3 Interfaces” section on
page9-20.
Step4 no shutdown Enable the port, if necessary. By default, user network interfa ces (UNIs)
are disabled, and network node interfaces (NNIs) are enabled.