Northbound connectivity from Fabric Interconnect can be achieved through a standard uplink, a port channel, or vPC configuration. The recommended configuration for the northbound connectivity is through Nexus switches and configuring a vPC.

The vPC configuration aggregates bandwidth and provides redundancy across two physical northbound Nexus switches to each Fabric Interconnect. In the vPC configuration, northbound Nexus switches logically appear as a single entity to Fabric Interconnect. A MAC address learned by an individual Nexus switch is shared between both switches.

vPC consists of the following components:

• Two peer Nexus switches: One is configured as primary and the other is configured as secondary
• vPC domain ID: This is a logical ID assigned to vPC and should be unique for Link Aggregation Control Protocol (LACP) negotiations
• vPC peer link: This is a high throughput link configured between the two Nexus switches for synchronizing the forwarding of information and data movement, if needed
• vPC keep alive link: This is configured between two Nexus switches for sharing heartbeat information
• vPC member links: These are southbound links to Fabric Interconnects:

To enable the vPC feature on Nexus switches, use the following steps:

1. The vPC feature needs to be enabled on Nexus switches. Also enable the LACP feature for port trunking:

        switch(config)# feature vpc
        switch(config)# feature lacp

 These features should be enabled on both switches.

2. Configure the vPC domain ID:

        switch(config)# vpc domain 1

 The domain ID should be configured on both switches.

3. Configure peer-keepalive:

        switch(config-vpc-domain)# peer-keepalive destination x.x.x.x

 peer-keepalive is also configured on both switches where the destination IP is usually the  management port IP of the peer switch, which is used as a heartbeat link for vPC.

4. Configure the peer link between directly connected ports of both switches:

        switch(config)# interface ethernet 1/10-11
        switch(config-if-range)# channel-group 100 mode active 
        switch(config-if-range)# interface port-channel100
        switch(config-if)# switchport mode trunk
        switch(config-if)# switchport trunk allowed vlan x

5. Create a port channel on both switches, enable the trunk mode, and allow the required VLANs:

        switch(config-if)# vpc peer-link

 Enable the port channel as the vPC peer link.

6. Configure Nexus member ports connecting to Fabric Interconnects:

        switch(config)#interface ethernet1/1-2
        switch(config-if-range)#channel-group 200
        switch(config-if-range)#interface port-channel200
        switch(config-if)#switchport mode trunk
        switch(config-if)#switchport trunk allowed vlan x
        switch(config-if)#vpc 200

 Similar configuration is required for vPC 200 on the second Nexus switch connectivity to the same  FI.

7. Now configure the second vPC on both switches for connecting to both Fabric Interconnects:

        switch(config)#interface ethernet1/3-4
        switch(config-if-range)#channel-group 201
        switch(config-if-range)#interface port-channel201
        switch(config-if)#switchport mode trunk
        switch(config-if)#switchport trunk allowed vlan x
        switch(config-if)#vpc 201

A similar configuration is required for vPC 201 on the second Nexus switch connectivity to the same FI.