A network consultant must design a high availability interconnection of a clustered Cisco UCS Fabric Interconnect toward two upstream Layer 2 switches. The Ethernet interconnection must use all redundant links and have no impact on the STP domain size. Which connectivity solution must be used?

Cisco UCS Fabric Interconnects in End-Host Mode (EHM) do not participate in Spanning Tree Protocol (STP), thus having no impact on the upstream STP domain size. In EHM, the Fabric Interconnect acts like a server with multiple NICs to the upstream network. To achieve high availability and use all redundant links, multiple uplinks from each Fabric Interconnect are bundled into a port channel. The upstream switches would be configured with a corresponding port channel (or vPC for dual-switch redundancy), allowing all links to be active and providing load balancing and failover.

A. Switch mode makes the Fabric Interconnect a full Layer 2 switch, which runs STP and directly impacts (increases) the STP domain size.
B. Switch mode runs STP, which is explicitly disallowed by the requirements. A single uplink also limits bandwidth and redundancy.
C. While End-Host Mode is correct, using only a single uplink toward each switch does not meet the requirement to use all redundant links if more are available.

1. Cisco, "Cisco UCS Manager Network Management Guide, Release 4.1", LAN Connectivity, Fabric Interconnects as End-Hosts. "In end-host mode, the fabric interconnect does not run the Spanning Tree Protocol (STP). Therefore, you do not need to consider the fabric interconnect for the STP domain."

2. Cisco, "Cisco UCS B-Series Servers and Cisco UCS C-Series Servers with Cisco Nexus 9000 Series Switches ACI Mode Design Guide", Cisco UCS Fabric Interconnect Connectivity, Section: End-Host Mode. "In EHM, the Cisco UCS Fabric Interconnect is not a switch. From the perspective of the upstream LAN switches, the fabric interconnect looks like a server with a large number of NICs."

3. Cisco, "Cisco UCS 6400 Series Fabric Interconnects Data Sheet", Product specifications. "The fabric interconnects can be deployed in a clustered active-active mode for high availability. This mode allows the fabric interconnects to be connected to the upstream network using a virtual PortChannel (vPC)."