I85PREP
⌘ K
Extreme Networks Associate (ECA) study materials
Extreme Networks Associate (ECA) study resources

Extreme Networks Associate (ECA): Fabric and Overlay Networking Concepts

Extreme Networks Associate (ECA) · Work through your exam, one topic at a time.

All guide sections

Fabric and Overlay Networking Concepts

Fabric and overlay questions test Shortest Path Bridging as Extreme implements it, the identifiers that make it work, and how it compares with EVPN/VXLAN overlays.

Fabric Connect basics

  • The fabric runs IS-IS (IEEE 802.1aq SPB) between NNI ports; every fabric link forwards and equal-cost paths are used.
  • Two identifiers matter and are constantly confused: the B-VID (backbone VLAN, commonly 4000) tags the transport, and the I-SID identifies a service instance such as a VLAN.
  • An L2 VSN maps a VLAN to an I-SID; an L3 VSN adds a virtual router; IP shortcuts let a fabric edge route into the core without a full L3 VSN on every node.
  • Provisioning happens at the edge only: core switches need no per-service configuration, which is the operational point of the design.

Fabric Attach

  • Fabric Attach lets an access switch or AP signal its VLAN and I-SID requirements to the fabric over LLDP, so the FA server provisions the UNI automatically.
  • FA elements include Universal switches and access points; the fabric edge acts as FA proxy or server and owns the mapping.

Redundancy

  • VSPs pair with vIST and use SMLT/RSMLT so both chassis forward traffic and can share a gateway IP.

Overlay comparison

  • EVPN/VXLAN is a routed underlay (OSPF or BGP) with a BGP EVPN control plane and VNIs; it is the data center norm and needs MTU headroom.
  • SPB is the campus and DCI choice where plug-and-play service provisioning and per-service isolation matter more than BGP policy control.

Worked example

A closet switch must carry VLAN 10 across the fabric. Reasoning: on the FA server, VLAN 10 maps to I-SID 100010; the closet becomes an FA element, so its port is auto-provisioned at the UNI; NNIs carry the service over B-VID 4000. No core switch is touched, which is exactly the design intent.

Traps

  • Swapping B-VID and I-SID in an answer.
  • Assuming STP still runs inside the fabric.
  • Believing an L3 VSN requires configuration on every transit node.
  • Forgetting that a UNI is customer-facing and an NNI is fabric-facing.