VMware SD-WAN Edge link selection behavior under specific scenarios.
Article ID: 330715
Updated On:
Products
Issue/Introduction
When traffic from VMware SDWAN Edge is sent via overlay (VCMP tunnels), the Dynamic Multipath Optimization (DMPO) protocol is used for link selection.
This article provides clarification on how VMware SDWAN Edge link selection works under specific scenarios. It covers basic info on how DMPO works. Please refer to VMware SD-WAN Dynamic Multipath Optimization (DMPO) for in depth knowledge on DMPO.
When traffic is being routed via Multi-path, DMPO protocol will chose the link with lowest latency (to break the tie) when more than one link is under same QoE band (green, yellow, red).
When traffic is being sent via Direct or via direct CSS (or Non SD-WAN destination) IPSEC tunnel, DMPO protocol will not be used.
When traffic is being sent via Direct or via direct CSS (or Non SD-WAN destination) IPSEC tunnel, VMware SD-WAN Edge, will chose the link with most available downstream bandwidth (to break the tie) when more than one link is under same QoE band (green, yellow, red). In order to determine which QoE band link will be placed in, Edge takes into consideration the best performing path out of all paths towards VCGs and Hubs from the same link.
This algorithm stays same regardless of traffic type real-time, transactional, bulk. However, QoE thresholds for each traffic type will be different as we can see in the picture below. Bulk traffic has the most generous QoE thresholds.
Under biz policy rule, preferred link logic will not work for the link with loss more than 10% even though "error correct before steering" is set to loss more than 10%. With loss more than 10%, link will be marked Unstable, which supersedes preferred link logic.
Link selection Behavior when primary VCG is down in biz policy:
When Primary VCG tunnel is down, the 'V' route would marked false. Hence Business policy to send traffic via a specific interface(Not a wan link) then it would not have "v" route since Primary VCG tunnel is dead and uses other WAN or LAN static routes based on the metric and tries to send it over them. This is an expected behavior. Only with "v" or non-secure routes link steering would occur.
Environment
Resolution
Link Steering under specific scenario should be considered as it behaves differently with destination route chosen for the flow.
Additional Information
Feedback
