JNCIE-DC key terms

A BGP EVPN advertisement carrying a MAC address and its associated IP address, used to distribute endpoint reachability across the fabric so remote leaf switches learn MAC and ARP entries without flooding.

A BGP EVPN advertisement that carries an IP prefix, enabling Layer 3 reachability between tenants over the overlay without requiring a MAC entry for every host in the remote subnet.

A 24-bit identifier in the VXLAN header that scopes a Layer 2 segment across the IP underlay, allowing roughly 16 million isolated segments compared with the 4094 limit of VLAN IDs.

A tunnel endpoint that encapsulates and decapsulates VXLAN frames, mapping local VLANs to VNIs and sourcing or terminating the outer IP header toward remote endpoints in the fabric.

The configuration binding a local VLAN to a VNI on a VTEP, defining which Layer 2 segment a frame belongs to when it enters or leaves the VXLAN tunnel.

A design where every leaf switch shares the same virtual MAC and IP for a tenant gateway, so a host's default gateway is always local and mobility across racks requires no gateway change.

An inter-subnet routing model where the ingress and egress leaf both use VXLAN VNIs for routing, keeping the same encapsulation and VNI pair on both sides of the fabric for consistent policy.

An inter-subnet routing model where the ingress leaf routes into the destination VNI and the egress leaf bridges to the host, so the two leaves handle different VNIs and encapsulation roles.

The IP fabric that provides loop-free reachability between VTEP loopbacks, typically using eBGP or OSPF with ECMP, and must converge quickly and carry large MTU to support encapsulated traffic.

Equal-cost multipathing, the forwarding behavior that spreads traffic across several equally preferred next hops, giving the spine-leaf fabric its aggregate bandwidth and resilience to single-link failure.

A two-tier Clos design where every leaf connects to every spine and spines never connect to each other, yielding predictable latency, uniform bandwidth, and simple scale-out by adding leaves or spines.

A logical network built on tunnels across a physical underlay, carrying tenant Layer 2 and Layer 3 traffic independently of the addressing and topology used by the underlying routers and switches.

A BGP speaker that reflects EVPN routes between clients so the overlay control plane does not require a full mesh of sessions among all leaf switches.

A mechanism where several leaf switches share an Ethernet Segment Identifier and coordinate active-active attachment of a dual-homed server, using designated forwarder election to avoid duplicate flooded frames.

A unique identifier for a multihomed attachment, advertised in EVPN so remote peers understand which leaf switches provide the same Layer 2 access to a dual-homed host.

The elected leaf in a multihomed Ethernet segment responsible for forwarding broadcast, unknown unicast, and multicast traffic toward the host, preventing duplicate delivery from multiple leaves.

A proxy behavior where leaf switches answer address resolution requests from local knowledge distributed by EVPN, reducing broadcast and unknown flooding across the fabric.

A device that bridges a VXLAN segment to a traditional VLAN or external network, typically used at fabric borders or for connecting legacy equipment that cannot run a VTEP.

The set of technologies and designs that extend a data center's Layer 2 or Layer 3 domains to another site, using options such as EVPN over WAN, VXLAN tunnels, or Layer 3 handoff.

An extension of a Layer 2 segment across sites so hosts keep the same subnet and gateway, which simplifies migration but increases broadcast scope and failure blast radius.

A virtual routing and forwarding instance that keeps separate routing tables on shared hardware, providing tenant isolation at Layer 3 within the fabric and at handoff points.

The guarantee that traffic from one tenant cannot reach another's resources, enforced through separate VRFs, VNIs, and policy such as firewall rules or ACLs at the fabric edge.

The controlled import of routes from one VRF into another, used to reach shared services such as firewalls or DNS while keeping default tenant separation intact.

A set of rules that permits or denies traffic between endpoints or tenants, applied at leaf interfaces, in VRFs, or via service insertion, and often expressed as intent rather than device syntax.

Redirecting selected traffic through a firewall, load balancer, or other appliance in the fabric, often using policy-based routing or EVPN service chaining, without breaking tenant segmentation.

The need to size underlay links for the extra VXLAN headers so encapsulated frames do not fragment or drop, typically by raising interface MTU and adjusting TCP MSS on endpoints.

Broadcast, unknown unicast, and multicast frames that must be flooded to all interested endpoints in a segment, handled in EVPN fabrics by ingress replication or multicast trees.

A flooding method where the ingress VTEP sends a copy of BUM traffic to each remote VTEP that has members in the segment, avoiding a multicast underlay requirement.

Describing the desired end state of the network rather than the commands to reach it, letting an orchestrator compute and push device-level configuration while detecting drift.

A controller or management platform that builds and maintains the underlay and overlay configuration across many switches from a single model, handling provisioning, validation, and upgrades.

Any difference between the intended configuration held in an automation source of truth and what is actually running on a device, often caused by manual changes that break repeatability.

A structured data schema describing configuration and operational state for a network device, used by NETCONF and RESTCONF to make automation vendor-neutral and validated.

Protocols for programmatic device management that carry YANG-modeled data, with NETCONF using XML over SSH and RESTCONF using HTTP methods and JSON or XML payloads.

Streaming operational data from devices at high frequency to a collector, giving near-real-time visibility into interface, queue, and control-plane health beyond traditional polling.

Bidirectional Forwarding Detection, a lightweight protocol that detects path failures in milliseconds and triggers fast reconvergence for routing protocols or static routes in the fabric.

A capability that lets a router restart its control plane while continuing to forward traffic, with helpers holding routes until the restarting peer re-establishes sessions and reconverges.

Introducing a new fabric design into an existing production network, requiring coexistence, phased cutover, and careful handling of spanning tree and gateway placement.

A server with two links to different leaf switches that are both active, requiring EVPN multihoming or MLAG so the host sees a consistent Layer 2 topology and no loops.

A design where every leaf performs routing for its locally attached hosts, removing the need to hairpin inter-subnet traffic to a centralized pair of core switches.