Tagged: Resilience
6 posts · browse all tags
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SDWAN Resilience Part 1: Design and Assumptions
A multi-part deep dive into building a resilient Fortinet SD-WAN on a real, slightly unfashionable topology — HA FortiManager, dual hubs in active/standby, no DCI, and an independent DCE. Part 1 lays out the topology, the AS plan, and challenges the design choices up front.
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SDWAN Resilience Part 2: BGP on Loopback
Why we peer BGP on loopbacks instead of tunnel-interface IPs, the FortiOS dynamic-IPsec config that makes it work, the spoke-side reciprocal config, and why hub-to-hub iBGP is the wrong answer in a no-DCI active/standby topology.
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SDWAN Resilience Part 3: DC to DCE Routing — Static, OSPF, and BGP
The hub FortiGate has to glue the spoke overlay to the data-centre environment that hosts the services. Static, OSPF, and eBGP each work — but only two of them fail correctly when the DCE peering goes down on one DC and not the other.
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SDWAN Resilience Part 4: BFD and Convergence Tuning
Default BGP timers detect failure in three minutes. That's unacceptable for active/standby SD-WAN. This post is the timer-math: DPD vs BFD on tunnels, BFD-for-BGP, holdtime ratios, the Graceful Restart trade-off, and what convergence numbers each combination actually delivers.
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SDWAN Resilience Part 5: Performance SLAs and Service Steering
BGP and BFD catch every failure that takes a tunnel or session with it. They don't catch the failure where everything looks healthy at the network layer but the application is gone. That's the gap SD-WAN Performance SLAs fill — and the place where careful health-check design earns its keep.
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SDWAN Resilience Part 6: Building It Right — Full DCI and Dual-Active ADVPN
The first five parts defended a topology with real constraints. This final post is the version without those constraints — Fortinet's reference design: full DCI, dual-active ADVPN, iBGP between hubs, symmetric routing, ECMP across both paths. The full shebang.