Routing, Traffic Steering, and Path Selection
Routing fundamentals
EdgeConnect appliances run dynamic routing (BGP and OSPF) and support static routes. Know route redistribution between LAN routing and the overlay, and how BGP is commonly used to advertise prefixes across the fabric. A frequent trap is asymmetric routing caused by multiple paths with equal preference; the appliance may forward return traffic on a different link, breaking stateful inspection.
Business intent and traffic steering
Business Intent Overlays (BIOs) express policy in business terms (application, site, user group) and map to traffic classes with ordered path selection criteria: preferred link, fallback order, and thresholds for latency, loss, and jitter. Per-packet versus per-flow steering changes behavior on degradation: per-packet spreads flows across links, per-flow keeps a flow on one link until it fails. Application identification (DPI) feeds the policy match; encrypted or unknown traffic falls to a default class.
Path selection mechanics
The appliance continuously measures link quality via probes and SLA thresholds. When the preferred path violates the SLA, traffic moves to the next qualifying path; when it recovers, traffic can move back. Forward error correction and packet duplication protect real-time flows, and quality of service queues enforce priority. Traps: assuming failover is instant (probe intervals matter), and assuming DPI identifies every app (it may not, so define a default).
Rule of thumb
Write BIOs top-down: match application, assign traffic class, list preferred then backup paths, then set SLA thresholds. Example: voice matches by DPI, class real-time, prefer MPLS, fall back to internet, threshold loss <1% and latency <150 ms.