Cisco Nexus 5000 Series - vPC as PIM Designated Router

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2-12
Cisco Nexus 5000 Series NX-OS Interfaces Operations Guide, Release 5.0(3)N2(1)
Chapter 2 Cisco Nexus 5500 Platform Layer 3 and vPC Operations
Using a vPC Switch as a Designated Router (PIM DR)
Using a vPC Switch as a Designated Router (PIM DR)
This section includes the following topics:
• DR Election and Source Registration, page 2-12
• Multicast Data Forwarding, page 2-12
DR Election and Source Registration
In vPC topologies, a DR election occurs based on the DR priority and the IP address. The elected DR is
responsible for sending the source registration toward the RP. When multicast traffic from a directly
connected source is received by the non-DR peer switch, the peer switch notifies the DR switch using a
Cisco Fabric Services (CFS) message about the source and group address. The DR generates source
registration packets to the rendezvous point (RP).
Multicast Data Forwarding
The Cisco Nexus 5500 Platform switch implements a dual-DR mechanism where both vPC peer switches
can forward multicast traffic from directly connected sources. The data forwarding rules are as follows:
• The peer switch receives multicast packets from a directly connected source, performs an mroute
lookup, and replicates packets for each interface in the OIF list.
• If the OIF is a VLAN trunked over a vPC peer link, one copy is sent over to the peer link for each
VLAN that is present in the OIF list. By default, the vPC peer link is considered an mrouter port.
Therefore, the multicast packets are sent over to the peer link for each receiving VLAN. You can use
the no ip igmp snooping mrouter vpc-peer link command to avoid sending multicast traffic over
a peer link for each receiver VLAN when there are no orphan ports.
This example shows how to avoid sending the multicast traffic in this scenario:
switch-Layer 3-1(config)# no ip igmp snooping mrouter vpc-peer link
Warning: IGMP Snooping mrouter vpc-peer link should be globally disabled on peer VPC
switch as well.
switch-Layer 3-1(config)#
With the above CLI configured, the multicast packet is only sent to peer link for VLANs that have orphan
ports.
This example shows how to display the list of all orphan ports:
switch-Layer 3-1# show vpc orphan-ports
Note:
--------::Going through port database. Please be patient.::--------
VLAN Orphan Ports
------- -------------------------
1 Eth1/15
switch-Layer 3-1#