OpenStack Foundation details conditions for live VM migration on SONiC EVPN-VXLAN
A new vendor brief describes how to run OpenStack live VM migration over an EVPN-VXLAN data center network built with SONiC, focusing on conditions that keep MAC/IP reachability and gateway behavior stable during host moves. The document matters for enterprise IT and security teams planning highly available virtualization and predictable traffic handling across network and compute domains.
Research Overview
The post explains live migration requirements in EVPN-VXLAN fabrics, emphasizing that VM memory and state move with the VM while the network must preserve Layer 2 connectivity and maintain reachable IP and default gateway information. It frames the approach as coordinated work across OpenStack compute and Neutron-based virtual networking, along with updates and behavior in the EVPN physical fabric.
It also presents validation considerations using FTAS, including a set of automation test cases intended to measure behavior across normal, load, and failure scenarios for a SONiC-based EVPN/VXLAN deployment.
Key Findings
The brief states that seamless migration depends on consistent EVPN and VXLAN parameters across source and destination compute nodes, including matching EVPN instance (EVI) and VXLAN network identifiers (VNI). It further highlights conditions for gateway consistency and host-independent Layer 2 reachability so the VM maintains continuity for MAC/IP learning and forwarding.
For the migration workflow, the post describes a sequence that starts with Nova initiating memory copying and Neutron configuring the destination interface, followed by EVPN MAC mobility updates and ARP/ND refresh signaling. It concludes with cleanup steps on the source side after traffic is redirected to the destination VTEP.
Technical Breakdown
The document lists preconditions for migration within EVPN-VXLAN fabrics, including consistent EVI/VNI membership on SONiC leaf switches and consistent VLAN-to-VNI mappings. It also requires anycast gateway consistency, with leaf switches advertising the same gateway IP and MAC for the tenant subnet.
It adds that compute-facing leaf switches must participate in the same EVPN instance and that VM MAC addresses must be learned and advertised using EVPN Type-2 (MAC/IP) routes, with immediate MAC/IP binding movement from the source to destination leaf. The brief also calls for VTEP and MTU consistency, stating that all compute-connected SONiC leaf switches must support VXLAN encapsulation and decapsulation and that the underlay MTU must accommodate VXLAN overhead.
Operational Impact and Validation
During migration, the post describes Nova triggering live migration and completing memory page transfer before interface activation on the destination host. It then describes Neutron and OVS/OVN associating a new virtual interface with the tenant VNI, with the destination leaf discovering the VM MAC on the new server-facing port.
For fabric updates, it describes EVPN Type-2 route updates via BGP EVPN, including a MAC mobility event and a resulting convergence time reported as less than 100ms. It also describes sending gratuitous ARP (IPv4) or unsolicited neighbor advertisements (IPv6) to refresh ARP/ND tables and reduce stale MAC-to-IP mappings, then redirecting VXLAN traffic to the remote leaf and performing source compute cleanup by deassociating VM interfaces and revoking expired EVPN Type-2 routes.
The post includes a conceptual mapping of VMware vMotion to OpenStack live migration and corresponding elements, and it outlines FTAS automation test cases. These cases include validating basic migration with shared storage, checking stability under CPU and memory load, ensuring network continuity for Layer 2 and Layer 3 connectivity, validating concurrent migrations, testing graceful failback using an abort workflow, and performing fabric-level EVPN/VXLAN validation involving timely MAC/IP withdrawal and avoidance of traffic black-holing.
Overall, the brief describes a coordinated OpenStack-to-network workflow for live VM migration over EVPN-VXLAN built on SONiC, along with network and fabric conditions designed to keep MAC/IP mobility and gateway behavior stable during movement. Blog Signals brief is a fact-based summary of the vendor blog.
Source: aviznetworks.com, by Khurram Khani, Vishwas Tiwari.