Hello. I am installing a pair of 93180 Nexus switches in vPC mode that will serve as connections for some new video servers. The Nexus switches will uplink to an existing 4500 core. We have been told that they want to use PIM-SM for multicast and that the 4500 core will be the RP. I am a bit unsure of exactly what commands I need on the 93180 switches to make this work.
I know I must enable the PIM feature but that's about it. Most guides I have read show a lot of interface level commands. The only SVI will be the mgmt interface and nothing else so the switch will just be layer 2. Can anyone tell me what I need to do here? Is it as simple as enabling IGMP and adding the pim-sparse commands to the links facing the servers and trunk links facing the core? Do I need to enable multicast routing globally?
If the Cisco Nexus switches are configured to act as Layer 2 switches, then you will only need to be concerned about whether IGMP Snooping is running on the Nexus switches. As Dawei mentioned, IGMP Snooping is enabled on Nexus switches by default, so the only configuration change you need will be to enable PIM Sparse Mode on the relevant SVIs of the Catalyst 4500 switches.
Configuring a default static route on the Nexus switches for management purposes does not change whether you need PIM configuration on the Nexus switches or not. If the Nexus switches are not the gateway for these VLANs and does not have a Layer 3 interface (e.g. an SVI) in these VLANs, then no PIM configuration is needed on the Nexus switches.
PIM feature works for layer3 multicast, if it just pure layer 2 switch, you don't need enable any feature or configuration. Nexus switch will enable igmp snooping automatically, you just need make sure configured "ip pim spare-mode" under SVI on c4500 Core switches.