Shortest Path Bridging (SPB) and Protocol Independent Multicast (PIM) cannot interoperate with each other on the switch at the same time. To ensure that SPB and PIM stay mutually exclusive, use the boot flag called spbm-config-mode:
The spbm-config-mode boot flag is enabled by default. This configuration enables you to configure SPB and IS-IS, but you cannot configure PIM either globally or on an interface.
If you disable the boot flag, you can configure PIM and IGMP Snooping, but you cannot configure SPB or IS-IS.
Important
Any change to the spbm-config-mode boot flag requires a reboot for the change to take effect.
If you plan to disable the boot flag, remove all SPB configurations first.
If you plan to use the default (enabled) setting, remove all PIM configurations first.
Simplified Virtual-IST (vIST) is for conventional network deployments that use SMLT and not SPB. The Simplified vIST feature provides a single CLI command to enable the virtual IST for SMLT deployments.
Simplified vIST is available ONLY for conventional multicast deployments with PIM and IGMP when the boot flag (spbm-config-mode) is disabled.
When the boot flag is enabled (default setting), Simplified vIST is not available. This means that you continue to configure SPB/IS-IS for vIST.
Simplified VIST requires that the two vIST devices be directly connected.
Note
PIM is supported with Simplified vIST only, not SPB vIST. However, you do not have to configure Simplified vIST to run PIM or IGMP Snooping in a non-SMLT topology.
Do not configure LACP on SPB NNI MLT links or on the Simplified Virtual IST.
Do not configure ECMP in PIM Simplified vIST scenarios. Running PIM in a Simplified vIST environment with ECMP enabled may lead to incorrect behavior since there are multiple options in terms of choosing the upstream node towards a host or source. For example, since the path chosen cannot be predicted (it is determined by the downstream PIM neighbor), we may end up not adding the Virtual IST MLT port in the PIM mroute‘s outgoing port list on the joined interface if the PIM Join Prune Message was received on an alternative path, different from the interface the local router considers to be the correct upstream to the source.
Traffic loss can occur in such an environment. Do not enable ECMP in PIM vIST scenarios.
After you disable the spbm-config-mode boot flag, you can configure PIM or IGMP Snooping on any VLAN including the vIST VLAN.
To configure the boot flag and Simplified vIST, see Configuring IP multicast in SMLT topologies or Configuring multicast on the switch.
Do not configure an RP or BSR on the vIST VLAN because you cannot ping them outside of the vIST VLAN subnet. When you enter the ip pim enable command on the vIST VLAN, the following message displays:
WARNING: Please do not use virtual IST VLAN IP address for BSR and RP related configurations, as unicast packets to virtual IST vlan IP address from outside of virtual IST vlan subnet will be dropped. Use Loopback or CLIP interface IP address for BSR and RP related configurations.