OPERATIONAL DEFECT DATABASE
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In a vPC topology with at least two Nexus 9K vPC peers comprising vPC pair (was found in a double-sided vPC scenario), when the IGMP snooping is enabled on one N9K vPC peer and disabled on the other N9K vPC peer (i.e. configuration of the IGMP snooping is asymmetric), in some conditions the IGMPv3 Reports and Queries received over a vPC may be reflected back to this vPC. For this to occur, the IGMP packet must be received by the vPC peer with IGMP snooping enabled and then sent (via CFSoE) over a Peer-Link (MCT) to the vPC peer who has IGMP Snooping disabled. In that case, such IGMP packets are being reflected by the N9K vPC peer who has the IGMP snooping disabled. This causes MAC flapping on the downstream devices (attached via vPC to the N9Ks) and, in turn, intermittent connectivity loss for affected MAC addresses. Symptoms looks similar to the L2 loop, although it's not a loop per se, but a packets reflection.
- NX-OS 7.0(3)I3(1) - Nexus 9000 (with Broadcom T2 ASIC)
Make the configuration of the IGMP snooping on both vPC peers identical (either globally, or on a per VLAN basis) - i.e. either disable IGMP snooping on both vPC peers, or enable it on both vPC peers, depending on the design requirements.
vPC requires the IGMP snooping configuration to be identical on both peers. This is a platform limitation and will be documented
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