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:
- 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.
- Configure the vPC domain ID:
switch(config)# vpc domain 1
The domain ID should be configured on both switches.
- 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.
- 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
- 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.
- 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.
- 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.