Multi-Homing with VPC

Multihoming with VPC

In this chapter we will learn how vPC works with VXLAN BGP EVPN fabric. In order to understand this concepts, let’s look below VXLAN BGP EVPN vPC topology with IP addressing .

Based on above topology , lets see the VPC Configuration

vPC Configuration

there are two vPC VTEP switches Leaf-102 and Leaf-103. Inter-switch links, vPC related link terms and IP addressing and Port Channel numbering can be seen from the below figure

In order to configure vPC , first we have to enable the vPC and LACP feature on Cisco Nexus device and then configure vPC .

Here ,  vPC domain 23 was created . VPC peer switches will automatically create a unique vPC system MAC address. The vPC system MAC address has a fixed part = 0023. 04ee.be.xx and the two last digits (xx) are taken from vPC domain ID. Our example vPC domain has ID 23, which HEX format is 17. So the vPC system address in our example will be 0023. 04ee.be17.

Now Configure the Port-channel and its related vPC configuration on Port-channel.

Once vPC is configured, lets understand the VXLAN Configuration, Its Control Plane and Data Plane Working .

VTEP Redundancy with vPC

When vPC is implemented into VXLAN fabric, both vPC VTEP peers start using a Virtual IP (VIP) address as a source address instead of their physical IP address (PIP). This also means that BGP EVPN starts advertising both Route Types 2 (MAC/IP advertisement) and 5 (IP prefix-route) with VIP as a next-hop (default behavior). There are two IP addresses configured into Loopback 0 interface, Primary IP 192.168.100.102/32 (PIP) and secondary IP 192.168.100.23/32 (VIP) in our example , as shown in below figure

First, configure the same secondary IP address 192.168.100.23 under the Loopback 0 interface on both vPC VTEP switches. An example is taken from VTEP-102. At this phase, that is the only change for the current configuration.

vPC VXLAN BGP EVPN Control Plane

Phase-1: Host Cafe boot up and sends a Gratuitous ARP message to verify the uniqueness of its IP address and inform the location of its own MAC address. Channel hash algorithm selects the interface g0/1 and the broadcast messages are sent out of it.