Vlag With Pim; Traffic Forwarding - Lenovo RackSwitch G8264 Application Manual

VLAG with PIM

Traffic Forwarding

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G8264 Application Guide for ENOS 8.4
Protocol Independent Multicast (PIM) is designed for efficiently routing multicast
traffic across one or more IPv4 domains. PIM is used by multicast source stations,
client receivers, and intermediary routers and switches, to build and maintain
efficient multicast routing trees. PIM is protocol independent; It collects routing
information using the existing unicast routing functions underlying the IPv4
network, but does not rely on any particular unicast protocol. For PIM to function,
a Layer 3 routing protocol (such as BGP, OSPF, RIP, or static routes) must first be
configured on the switch.
Lenovo Enterprise Network Operating System supports PIM in Sparse Mode
(PIM‐SM) and Dense Mode (PIM‐DM). For more details on PIM, see Chapter 36,
"Protocol Independent Multicast."
PIM, when configured in a VLAG topology, provides efficient multicast routing
along with redundancy and failover. When the multicast source is located in the
core L3 network, only the primary VLAG switch forwards multicast data packets
to avoid duplicate packets reaching the access layer switch. The secondary VLAG
switch is available as backup and forwards packets only when the primary VLAG
switch is not available and during failover. When the multicast source is located in
the L2 domain, behind the VLAG ports, either the primary or the secondary switch
will forward the data traffic to the receiver, based on the shortest path detected by
PIM.
See Figure 19 on page 215 for a basic VLAG topology. For PIM to function in a
VLAG topology, the following are required:
IGMP (v1 or v2) must be configured on the VLAG switches.

 A Layer 3 routing protocol (such as BGP, OSPF, RIP, or static routes) must be
globally enabled and on VLAG‐associated IP interfaces for multicast routing.
 The VLAG switches must be connected to upstream multicast routers.
 The Rendezvous Point (RP) and/or the Bootstrap router (BSR) must be
configured on the upstream router.
 The multicast sources must be connected to the upstream router.
 Flooding must be disabled on the VLAG switches or in the VLAN associated
with the VLAG ports.
ISL ports must be members of VLANs that have VLAG ports as members.

For PIM configuration steps and commands, see "PIM Configuration Examples"
on page 593.
In a VLAG with PIM topology, traffic forwarded by the upstream router is
managed as follows when the multicast source is located in the core L3 network
and the receiver is located in the L2 network:
 If the primary and secondary VLAG ports are up, the primary switch forwards
traffic to the receiver. The secondary switch blocks the traffic. Multicast entries
are created on both the VLAG switches: primary VLAG switch with forward
state; secondary VLAG switch with pruned state.