Neutron SVI Integration Overview
A Switched Virtual Interface (SVI) is a virtual local area network (VLAN) of switch ports that have a single interface to a routing or bridging system. In the context of a Layer 3 Out (L3Out) configuration, you configure an (SVI) to provide connectivity between the Cisco Application Centric Infrastructure (ACI) leaf switch and a router.
By default, when you configure a single L3Out with SVI interfaces, the VLAN encapsulation spans multiple nodes within the fabric. The spanning occurs because the Cisco ACI fabric configures the same bridge domain (VXLAN VNI) across all the nodes in the fabric where the L3Out SVI is deployed. The bridge domain configuration occurs as long as all SVI interfaces use the same external encapsulation (SVI). However, when different L3Outs are deployed, the Cisco ACI fabric uses different bridge domains even if they use the same external encapsulation (SVI).
Beginning with Cisco Application Policy Infrastructure Controller (APIC) Release 5.1(1), Cisco APIC supports a dual stack on SVI networks; that is, it now supports IPv6 and IPv4 connections. This feature enables Border Gateway Protocol (BGP) peering over L3Outs for IPv6 routes and IPv4 routes if you enable them. See the section Configure SVI Integration with Dual-Stack IP Addressing.
Beginning with Cisco APIC Release 5.1.(1), you can enable the Neutron SVI feature for VMs on OpenStack compute nodes using the OpFlex agent as well as the community OVS agent. This feature is only available in the unified mode with the AIM based plug-in.
When an OpenStack cluster is integrated with Cisco ACI through the Cisco ACI Modular Layer 2 (ML2) plug-in, you can create a floating L3Out that dynamically instantiates SVIs on Cisco ACI border leaf switches to peer with the OpenStack workload. In the Cisco ACI naming convention, this function is called Neutron SVI. The Neutron SVI feature allows you to configure in OpenStack Neutron networks that automatically create Cisco ACI L3Out, which potentially can enable BGP peering.
The OpenStack administrator can bind OpenStack virtual network functions (VNFs) directly to those Neutron networks. The Cisco ACI ML2 plug-in for OpenStack dynamically creates and deletes the SVI configuration on the L3Out to peer BGP with the VNFs that are created or destroyed. You can create an SVI network without specifying the L3Out. In that case, the plug-in automatically creates it and establishes the mapping.
Reasons for Configuring SVIs
SVIs are configured for a VLAN for the following reasons:
To allow BGP peering between virtual machines (VMs) peering with the (L3Out)
To use the upstream OpenStack API to control L3Out node profiles
To enable the OpenStack API to create an L3Out configuration on Cisco ACI.
SVI advantages include:
Configuration of the dynamic routing protocol between fabric switch and VNFs
Support for dynamic and distributed VNFs even across multiple Cisco ACI pods
Equal-cost multipath (ECMP) traffic distribution among VNFs
Optimal performance with VNFs
Distributed route peering between the switches and OpenStack VNFs
The Cisco ACI plug-in for OpenStack enables the route peering based on the creation or destruction of VNFs. The Neutron SVI feature dynamically and automatically creates and destroys the SVI on the underlay. The feature also enables line rate routing capabilities and up to 64-way ECMP to the VNFs.
Neutron SVI supports up to six pairs of switches under same L3out. Supports VNFs across distributed sites (multipod) and bonding with VPC to fabric with bidirectional forwarding detection (BFD) for fast VM failure detection.