The Art of Making Vendors Agree: Lessons from Interoperability Testing#

Patrick Prangl (Arista)

• Why: Directly relevant to running multi-vendor DC fabrics. It explains how EANTC's Berlin interop event works, what actually failed when vendors met, and what the 2026 test scope says about where DC/SP technology is heading (EVPN-VXLAN, SR-MPLS/SRv6, and a brand-new AI/UEC testbed).
• What: An operator-usable guide to reading the EANTC interoperability report — plus concrete failure examples from the 2026 event, including malformed IS-IS TLV 222 (MT routing, RFC 5120) that led to corrupted LSPs, missing SRv6 Capability TLV 25 breaking backup-path calculation, and TI-LFA initially steering SRv6 routes to DROP. Also useful maturity signals: OISM (overlay multicast) control planes converge but data planes diverge; NOS-only vendor participation is shrinking.
• How: Multi-vendor test beds (EVPN-VXLAN, EVPN-SR, MPLS-SR, SRv6, SDN/PCEP) run over two weeks with EANTC-validated results; the report only includes successful tests, and config/image details are reported to EANTC but not published. The talk walks through how ambiguous RFC language ("SHOULD", reserved bits) turns into real interop bugs.
• Where applicable: The EANTC report and methodology are vendor-neutral and freely usable by anyone doing DC fabric procurement or PoCs. Speaker is an Arista systems engineering lead, so the framing leans toward a participant's perspective, but the content is the test event, not a product pitch. Explicit caveat from the speaker: passing interop tests does not replace your own PoC.