Many documents say that you can use an SVI as a vPC keepalive link, but they don’t show how to accomplish this. Usually they show the keepalive link using the MGMT0 port. Here is an example of using an SVI for the vPC keepalive link.
The keepalive link will be a physically different port and connection between the Nexus5k’s than the peer link. So for example if you are using interface e1/1 and e1/2 on both sides of the Nexus5k’s for the peer link, then you would use e1/3 for the keepalive link.

<strong>Configuration Nexus 5596 Switch 1</strong>
vlan 80
name VLAN-KeepAlive
exit
!
interface Vlan900
ip address 1.1.1.1/30
no shutdown
!
vpc domain 1
peer-keepalive destination 1.1.1.2 source 1.1.1.1 vrf default
exit
!
interface Ethernet1/3
description To-5596-Eth1/3-VPC-KeepAlive
switchport mode trunk
switchport trunk allowed vlan 80
no shut
exit
!

<strong>Configuration Nexus 5596 Switch 2</strong>

vlan 80
name VLAN-KeepAlive
exit
!
interface Vlan80
ip address 1.1.1.2/30
no shutdown
!
vpc domain 1
peer-keepalive destination 1.1.1.1 source 1.1.1.2 vrf default
exit
!
interface Ethernet1/3
description To-5596-Eth1/3-VPC-KeepAlive
switchport mode trunk
switchport trunk allowed vlan 80
no shut
exit
!

<strong>Note</strong>

You must make sure that the vPC peer link does not allow your vPC keepalive VLAN over its trunk. You cannot have the “heartbeats” going over two different links. If you have your peer link trunk set to allow all VLANS, the keepalive link will never come up which will keep the peer link from coming up.