What is a Software Engineer?
A Software Engineer at Arista Networks builds the foundation that powers the world’s most demanding networks. You will develop features in Arista EOS (Extensible Operating System)—our Linux-based network operating system that runs across data center, routing, and campus platforms—and contribute directly to how packets are forwarded, routes are computed, interfaces are managed, and systems are tested at hyperscale.
This role has a uniquely high impact. Your code will be deployed in cloud providers, AI clusters, and large-scale enterprises, where performance, correctness, and reliability are non-negotiable. You will work in C/C++ and Python on Linux, implement and optimize L2/L3 features, collaborate with hardware teams on Layer1/PHY integration, and own projects end-to-end—from requirements and design through automated testing, release, and customer support.
What makes this role compelling is the combination of deep systems engineering, real protocol and device-level interactions (BGP, OSPF/IS-IS, EVPN/VXLAN, PHY/optics), and an engineering-driven culture that expects you to lead with technical rigor. If you want to build software that moves the internet and AI fabrics, this is where you do it.
Getting Ready for Your Interviews
Your interviews will probe how you think, how you write software that works in production, and how you debug complex systems quickly. Expect a blend of coding in C/C++, core CS (data structures, OS, concurrency), and networking (L2/L3, TCP/IP, EVPN/VXLAN), along with discussions of design, testing, and ownership.
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Role-related Knowledge (Technical/Domain Skills)
Interviewers assess depth in C/C++, Python for tooling, Linux, and networking protocols. You demonstrate this by writing correct, memory-safe, testable code; explaining OS and networking trade-offs; and showing familiarity with EOS-like systems (routing, packet forwarding, device drivers, telemetry). -
Problem-Solving Ability (How you approach challenges)
You will be evaluated on decomposing ambiguous problems, selecting data structures/algorithms fit for scale, and balancing performance with maintainability. Think aloud, justify trade-offs, and show iterative validation (tests, assertions, logs). -
Leadership (How you influence and mobilize others)
Arista expects engineers to “lead from the code.” Interviewers look for initiative, technical judgment, and end-to-end ownership: writing specs, building test plans, mentoring peers, and handling escalations with customers. -
Culture Fit (How you work with teams and navigate ambiguity)
The bar includes honesty, clarity, and autonomy. Show that you can collaborate across software, hardware, test, and support; handle feedback; and operate with precision, pace, and quality in a small, high-output team.
Interview Process Overview
Arista’s interview experience emphasizes deep technical discussion with practicing engineers. You will notice strong alignment between questions and the actual work: writing C/C++ that runs on Linux, debugging complex interactions across protocols and hardware, and reasoning about performance and scale. The process is rigorous but respectful—interviewers aim to understand how you think under realistic constraints.
Expect efficient pacing. Some candidates see an initial coding assessment (e.g., a short, time-bound coding screen), while others move directly to live technical interviews. The philosophy is consistent: small teams, high agency, and a strong signal on quality. You will likely encounter coding, systems fundamentals (memory, threads, processes), networking (L2/L3, TCP/IP, EVPN/VXLAN), and a design/problem-solving conversation grounded in EOS-style components. Manager conversations focus on ownership, mentorship, and how you operate in production.
This timeline visualizes the typical progression from recruiter contact through technical screens, onsite/virtual panels, and decision. Use it to plan your prep cadence, block focused time for system design and coding practice, and prepare crisp examples for behavioral discussions. Keep momentum: confirm availability quickly, clarify expectations per round, and ask for any focus areas before each step.
Deep Dive into Evaluation Areas
Coding in C/C++ and Software Fundamentals
You will write C/C++ under realistic constraints: memory management, complexity targets, correctness, and testability. Expect to compile concepts you use daily—pointers/references, RAII, STL containers/iterators, time/space trade-offs—into clean implementations.
Be ready to go over:
- Core data structures/algorithms: arrays, strings, hash maps/sets, heaps, trees, graphs, sorting, searching
- C/C++ specifics: pointers, lifetimes, const-correctness, move semantics, smart pointers, exceptions vs. error codes
- Testing and correctness: unit tests, edge cases, invariants, input validation
- Advanced concepts (less common): lock-free structures, custom allocators, circular buffers, cache-aware designs
Example questions or scenarios:
- “Implement a rate limiter or LRU cache in C++ with O(1) operations and discuss thread-safety options.”
- “Parse a routing table dump into efficient in-memory structures; support longest-prefix match lookups.”
- “Given a packet header schema, encode/decode functions with robust bounds checking and tests.”
Systems: Linux, OS, Concurrency, and Performance
Arista software is systems software. You will be asked to reason about processes, threads, scheduling, memory, and I/O. Show that you can instrument code, analyze flame graphs or perf counters, and choose the right concurrency primitives.
Be ready to go over:
- Processes/threads: context switches, synchronization, deadlocks, condition variables, atomics
- Memory: stack vs heap, fragmentation, paging, NUMA basics, memory visibility
- I/O and performance: epoll/select, buffers, DMA basics, profiling
- Advanced concepts (less common): lock-free algorithms, memory barriers, copy-on-write, zero-copy I/O
Example questions or scenarios:
- “Design a multithreaded log aggregator; detail contention points and backpressure.”
- “Diagnose a memory leak or heisenbug in a long-running daemon; what tools and hypotheses?”
- “Compare polling vs. interrupt-driven I/O for a high-throughput task.”
Networking and Protocols (L2/L3, EVPN/VXLAN, TCP/IP)
You do not need to be a CCIE, but you should be comfortable with core concepts and data structures protocols rely on. Expect questions on packet paths, FIB/RIB, adjacency, timers, and failure handling at scale.
Be ready to go over:
- L2: VLANs, LACP, STP/RSTP/MST, MACsec basics
- L3 and routing: ARP/ND, OSPF/IS-IS, BGP, ECMP, convergence, route scaling
- DC fabrics: EVPN/VXLAN, MLAG, underlay/overlay, routing on the host
- Advanced concepts (less common): Segment Routing, telemetry/streaming, buffer management, QoS/PFC
Example questions or scenarios:
- “Explain EVPN route types and how MAC/IP mobility is handled.”
- “Design a control-plane approach to program 1M routes to a multi-ASIC chassis under tight time budgets.”
- “Trace a packet through an underlay/overlay fabric, pinpointing failure domains.”
System Design for Network Software (EOS-style Components)
Design interviews are grounded in real EOS problems: building a protocol module, a forwarding pipeline renderer, or a telemetry subsystem. Interviewers look for modularity, scale, observability, and failure handling.
Be ready to go over:
- APIs and abstractions: clean interfaces to hardware drivers and higher layers
- State and scale: in-memory models, snapshots, incremental updates, backpressure
- Resilience: process restarts, warm upgrades, hitless transitions, watchdogs
- Advanced concepts (less common): multi-ASIC partitioning, hardware offload orchestration, graceful in-service upgrades
Example questions or scenarios:
- “Design a BGP feature that supports fast failover and route dampening; outline data structures and timers.”
- “Build a packet forwarding state renderer for a router with hundreds of forwarding chips.”
- “Instrument a telemetry pipeline for link health and anomaly detection.”
Debugging, Testing, and Production Quality
Quality is a first-class deliverable. Expect to discuss how you write functional specs, test plans, and automated tests alongside the code. Be explicit about how you triage field issues and deliver confident fixes.
Be ready to go over:
- Test strategy: unit, integration, soak, fuzz; simulators and traffic generators
- Diagnostics and bring-up: board-level tests, link diagnostics, counters, PRBS
- Prod hygiene: feature flags, rollbacks, canaries, versioning
- Advanced concepts (less common): concurrency testing, determinism, fault injection
Example questions or scenarios:
- “Author a test plan for MACsec or LACP; include negative and scale cases.”
- “Given intermittent retransmissions at 400G, outline a methodical root-cause workflow.”
- “Design a diagnostic to validate a new PHY or optics module during manufacturing.”
This visual highlights the recurring emphasis on C/C++, Linux/OS, and Networking (BGP/OSPF/EVPN/VXLAN), with supporting themes like testing, diagnostics, and Python for automation. Use it to prioritize study time: double down on C/C++ fundamentals and networking control-plane concepts, then reinforce with system design and debugging workflows.
Key Responsibilities
You will design, implement, test, and ship features for Arista EOS and platform software—owning quality from spec to customer impact. The work spans core routing/forwarding, Layer1/PHY integration, diagnostics, platform management, and productivity tooling.
- Drive features in C/C++ and Python on Linux, write functional and design specs, and build automated tests and test infrastructure.
- Collaborate with hardware, manufacturing, and system test teams to bring new platforms to market and maintain high yields.
- Operate with production rigor: triage customer issues, build safe upgrades and rollbacks, and deliver maintainable fixes.
- Contribute across the stack as needed—packet forwarding, routing protocols, Layer2/Network Services, Network Systems, and Engineering Productivity—while mentoring peers.
You will frequently interface with Customer Support Engineers, product managers, and field teams to refine requirements, validate assumptions at scale, and ensure the software behaves predictably in the largest customer environments.
Role Requirements & Qualifications
Strong candidates pair systems fluency with networking fundamentals and a bias for quality. The essentials are clear:
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Must-have technical skills
- C/C++ on Linux/UNIX, with attention to memory, performance, and correctness
- Python for tooling, tests, and automation
- Core CS: data structures/algorithms, OS concepts, concurrency, I/O
- Networking basics: L2 (VLANs, LACP, STP), L3 (ARP/ND, OSPF/IS-IS, BGP), TCP/IP
- Testing/Debugging: unit/integration tests, gdb, sanitizers, tcpdump/Wireshark
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Experience expectations
- Experience ranges by level; roles include Software Engineer through Senior/Lead across EOS Routing, Layer1, Packet Forwarding, and Network Systems
- Demonstrated end-to-end ownership: specs, code, tests, deployment, and support
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Soft skills that differentiate
- Clear written and verbal communication, precise technical judgment, and mentorship mindset
- Calm, structured debugging and a collaborative approach with hardware and support teams
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Nice-to-haves (give you an edge)
- Deep knowledge of EVPN/VXLAN, Segment Routing, MACsec, or distributed systems
- Exposure to packet forwarding chips, PHYs/optics, or diagnostics/manufacturing test
- Experience with CI/CD, containers, build systems, performance tooling
This visualization summarizes compensation ranges shared across Software Engineering roles and locations at Arista. Expect base + bonus + equity, with ranges varying by level and market (e.g., Software Engineer roles around the mid-$100Ks base; Senior/Lead roles often higher). Align expectations with location and scope, and be prepared to discuss level calibration during the process.
Common Interview Questions
You will see a mix of coding, systems, networking, and behavioral prompts. Use these examples to structure targeted practice and to prepare crisp, testable solutions and narratives.
Coding / Algorithms (C/C++)
Focus on correctness, complexity, and safety. Write tests as you go.
- Implement a thread-safe bounded queue with blocking push/pop; discuss fairness and wakeups
- Build a prefix trie supporting insert, delete, and longest-prefix match for IPv4
- Parse and validate a custom packet header; handle malformed inputs and unit tests
- Implement LRU with O(1) ops and explain memory ownership and eviction invariants
- Merge K sorted streams efficiently; analyze memory and cache behavior
Systems (Linux, OS, Concurrency)
Expect to reason about processes, memory, and I/O under load.
- Diagnose a memory leak in a daemon; what tools and signals do you rely on?
- Compare mutexes, RW locks, and atomics in a high-read/low-write workload
- Design a log pipeline with backpressure and loss visibility
- Walk through epoll-based event loops; when to batch vs. prioritize latency
- Explain copy-on-write, page faults, and zero-copy I/O trade-offs
Networking (L2/L3, EVPN/VXLAN, TCP/IP)
You’ll connect protocol logic to data structures and timers.
- Contrast control plane vs. data plane responsibilities for BGP
- Explain EVPN route types and how MAC/IP mobility is handled
- How does ARP/ND interact with ECMP and neighbor churn at scale?
- Design health checks for MLAG peer links and recovery paths
- Trace a TCP handshake and where buffer pressure can arise on a switch
System Design / Architecture (EOS-style)
Design modular components that scale and degrade gracefully.
- Design a routing state renderer that programs multiple forwarding ASICs
- Build a telemetry service that streams interface health and counters
- Propose an in-service software upgrade mechanism with millisecond downtime
- Architect diagnostics for new PHY/optics bring-up in manufacturing
- Define clear HAL abstractions for platform sensors and power/fan controllers
Behavioral / Leadership
Demonstrate ownership, clarity, and collaboration.
- Tell me about a high-severity production issue you owned end-to-end
- Describe a time you influenced a design decision without formal authority
- How do you write and use test plans to prevent regressions?
- Share an example of mentoring or leveling up a teammate
- When did you push back on requirements to protect quality?
Use this interactive module on Dataford to practice questions by category, track progress, and benchmark against role expectations. Prioritize areas highlighted by your recruiter and tailor your drills to the specific team focus (e.g., Routing vs. Layer1 vs. Network Systems).
Frequently Asked Questions
Q: How difficult is the interview, and how much time should I allocate to prepare?
Plan 3–4 weeks of focused prep if you’re already comfortable with C/C++, Linux, and networking; 6–8 weeks if you’re ramping on networking. The bar is high but fair—interviews mirror the actual work and reward clarity, correctness, and pragmatic engineering.
Q: What makes successful candidates stand out at Arista?
They write clean, testable C/C++; reason crisply about OS and networking; and pair strong problem decomposition with production awareness (observability, rollbacks, failure modes). They also communicate precisely and own outcomes end-to-end.
Q: What is the culture like on engineering teams?
Engineering-driven, low-ego, and highly autonomous. Small teams ship impactful features, collaborate closely with hardware and support, and value written specs, solid testing, and customer empathy.
Q: How fast is the process, and when should I expect updates?
Timelines vary by role, but decisions typically follow promptly after onsite panels. Keep your recruiter informed of availability; ask for focus areas ahead of each round to prepare efficiently.
Q: Is the role remote or location-specific?
Arista has roles across multiple offices (e.g., Santa Clara, Austin, Nashua) with team-dependent flexibility. Confirm expectations for your target team and location during recruiter conversations.
Q: Do I need deep networking expertise to pass?
You need solid fundamentals and curiosity. Depth expectations scale with role (e.g., Routing/Packet Forwarding vs. EngProd). Be ready to reason about L2/L3 and DC fabrics; hands-on experience is a plus.
Other General Tips
- Code like it will ship: Use clear APIs, input validation, bounds checks, and small unit tests—even in interviews. This mirrors Arista’s production mindset.
- Narrate trade-offs: When optimizing, state the metric (latency, throughput, memory) and the impact of your choices. Interviewers reward explicit trade-off reasoning.
- Instrument early: Discuss how you’d add counters, logs, or traces to validate assumptions. Mention concrete tools (asan, perf, tcpdump).
- Protocol clarity: Use accurate terminology (e.g., EVPN route types, ARP vs. ND). If unsure, state assumptions up front and proceed methodically.
- Own the edge cases: Call out failure modes—timer storms, neighbor churn, buffer pressure, process restarts—and how you’d test them.
- Ask precise questions: Clarify constraints before coding. Confirm expected complexity, data sizes, and thread model to avoid rework.
Summary & Next Steps
As a Software Engineer at Arista Networks, you will build the systems that power AI fabrics, cloud providers, and mission-critical enterprises. This is high-leverage, high-ownership work in C/C++/Python on Linux, across routing, forwarding, Layer1, and platform software—delivered with production-grade quality.
Prioritize preparation around:
- C/C++ coding with tests and memory safety
- Linux/OS and concurrency fundamentals
- Networking (L2/L3, EVPN/VXLAN, TCP/IP) and EOS-style design
- Debugging/diagnostics and test planning with observable outcomes
Approach each interview like a real design/build/debug session: clarify constraints, write clean code, validate with tests, and explain how you would observe and roll back in production. Explore the interactive practice on Dataford to close gaps quickly and benchmark against the role.
You are capable of meeting this bar. Focus your effort, practice with intent, and bring the mindset of an engineer who ships reliable systems at scale. We look forward to seeing how you think—and how you build.