Arista Foundations cheat sheet

EOS is a Linux-based network operating system; the CLI runs in a Bash shell, so standard Linux tools (e.g., tcpdump, ip, grep) are available.

Configuration is stored in startup-config, running-config (active), and the rollback checkpoint repo; 'configure replace' and 'rollback' restore prior states.

EOS supports eAPI (JSON-RPC over HTTP/HTTPS) and OpenConfig/gNMI for programmatic management; eAPI runs on port 443 by default.

Management plane separation: out-of-band via Management1 interface or in-band via any routed/VRF interface; 'management api http-commands' enables eAPI.

MLAG uses a peer link (L2) plus a peer-keepalive (L3) link; both switches share a virtual MAC and present an aggregated port-channel to downstream devices.

VXLAN-GENEVE encapsulation with EVPN control plane provides Layer 2 extension over Layer 3; VTEPs are loopback interfaces in the underlay.

EOS image naming: EOS-4.x.yF is a feature release; 'M' denotes maintenance; 'F' denotes feature; 'I' denotes interim.

Zero Touch Provisioning (ZTP) bootstraps a switch via DHCP option 67/66 or USB; the script can pull config from CloudVision or a URL.

Leaf-spine topology: every leaf connects to every spine (full mesh), and spines never connect to each other; traffic is at most two hops leaf-to-leaf.

ECMP across spines provides load balancing; equal-cost paths are hashed by 5-tuple (src/dst IP, src/dst port, protocol) by default.

Oversubscription ratio = southbound (host-facing) bandwidth ÷ northbound (uplink) bandwidth; 1:1 is non-blocking, 3:1 is common for general compute.

MLAG is used at the leaf layer to dual-home servers; vPC (Arista term) pairs two leaves with a peer link and peer keepalive.

Underlay routing commonly uses eBGP with unique ASNs per leaf and a common spine ASN (or BGP unnumbered) to build loopback reachability.

Spine layer is typically fixed-form-factor high-radix switches; leaf layer may be ToR or middle-of-row depending on cabling and rack density.

Failure domain: a single spine failure reduces ECMP width but does not isolate leaves; a leaf failure isolates only its attached hosts unless MLAG is used.

Arista 7050X/7060X/7500R series are common leaf/spine platforms; 7500R is a modular chassis used for spine or super-spine roles.

CloudVision is a multi-tier platform: CVP (on-prem) or CVaaS (cloud SaaS); it provides change management, provisioning, telemetry, and compliance.

CloudVision uses the NetDB/state stream from EOS devices via TerminAttr agent; TerminAttr pushes telemetry and config state to CloudVision.

Change control workflows: configlets are attached to containers; tasks are generated and can require approval before deployment.

CloudVision Studios provide intent-based provisioning (e.g., L3 Leaf-Spine studio) that generates configlets from a declarative model.

Compliance dashboard compares running config against designed config and flags drift; remediation can be automated via change control.

CloudVision telemetry includes streaming OpenConfig/gNMI data for interface counters, queue depths, and hardware health; NetDB stores time-series data.

CloudVision supports role-based access control (RBAC) with local users or TACACS+/RADIUS integration; audit logs record all changes.

CloudVision can be deployed as a single-node or multi-node cluster; CVaaS removes the need for on-prem CVP infrastructure.

EOS supports BGP, OSPF, IS-IS, and static routing; BGP is the default underlay/overlay protocol in Arista leaf-spine designs.

BGP best-path selection order: weight, local preference, locally originated, AS path length, origin, MED, eBGP over iBGP, IGP metric to next hop, router ID.

EVPN route types: Type 2 (MAC/IP advertisement), Type 3 (inclusive multicast), Type 5 (IP prefix); Type 1 is Ethernet auto-discovery.

BGP unnumbered uses IPv6 link-local next hops over point-to-point links, eliminating per-link IP addressing in the underlay.

OSPF areas: backbone area 0; ABRs connect areas; EOS supports OSPFv2 (IPv4) and OSPFv3 (IPv6).

Route redistribution requires a route-map to control loops and metric propagation between protocols.

ECMP in EOS is enabled by default for BGP and OSPF up to the platform's max-path value (e.g., 64 or 128 paths).

VRF (virtual routing and forwarding) isolates routing tables; VRF-lite uses per-VRF routing without MPLS.

sFlow samples packets (1 in N) and exports to a collector; it provides flow visibility without full packet capture.

Arista CloudVision telemetry uses gNMI/OpenConfig streaming for near-real-time counters and state; TerminAttr is the on-device agent.

Port mirroring (SPAN) copies traffic to a destination port; ERSPAN encapsulates mirrored traffic in GRE for remote collectors.

Arista DANZ (Data Analyzer) enables advanced monitoring features on supported platforms, including flow-based filtering and timestamping.

MACsec provides Layer 2 encryption on point-to-point links; EOS supports MACsec on select platforms for inter-switch and host links.

Control-plane policing (CoPP) protects the CPU by rate-limiting exception traffic (e.g., BGP, SSH, ARP) to the control plane.

Arista NDR (Network Detection and Response) uses mirroring/telemetry to feed security analytics for threat detection.

TACACS+ and RADIUS provide AAA for device access; local fallback accounts should be configured for out-of-band recovery.