Fabric interconnect ports configured as uplink ports are used to connect to upstream network switches. You can connect these uplink ports to upstream switch ports as individual links or as links configured as port channels. Port channel configurations provide bandwidth aggregation as well as link redundancy.

You can achieve northbound connectivity from the fabric interconnect through a standard uplink, a port channel, or a virtual port channel configuration. The port channel name and ID configured on the fabric interconnect should match the name and ID configuration on the upstream Ethernet switch.

It is also possible to configure a port channel as a vPC, where port channel uplink ports from a fabric interconnect are connected to different upstream switches. After all uplink ports are configured, you can create a port channel for these ports.

Downlink Connectivity

Each fabric interconnect is connected to I/O modules in the Cisco UCS chassis, which provides connectivity to each blade server. Internal connectivity from blade servers to IOMs is transparently provided by the Cisco UCS Manager using the 10BASE-KR Ethernet standard for backplane implementations, and no additional configuration is required. You must configure the connectivity between the fabric interconnect server ports and IOMs. Each IOM, when connected with the fabric interconnect server port, behaves as a line card to fabric interconnect; hence, IOMs should never be cross-connected to the fabric interconnect. Each IOM is connected directly to a single fabric interconnect.

The Fabric Extender (also referred to as the IOM, or FEX) logically extends the fabric interconnects to the blade server. The best analogy is to think of it as a remote line card that’s embedded in the blade server chassis, allowing connectivity to the external world. IOM settings are pushed via the Cisco UCS Manager and are not managed directly. The primary functions of this module are to facilitate blade server I/O connectivity (internal and external), multiplex all I/O traffic up to the fabric interconnects, and help monitor and manage the Cisco UCS infrastructure. You should configure fabric interconnect ports that should be connected to downlink IOM cards as server ports. You need to make sure there is physical connectivity between the fabric interconnect and IOMs. You must also configure the IOM ports and the global chassis discovery policy.