Unexpected Suspension of PIM During Unified ISSU

You can minimize PIM traffic loss during the unified in-service software upgrade by issuing the ip pim dr-priority command to set a priority so that PIM neighbors do not forward traffic through the upgrading router. By default, a PIM interface has a priority of one. If you set the priority to one, the lowest possible priority, then the upgrading router is not selected to be a designated router in the PIM network if an interface on another router in that network has a higher priority.

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