Arista Routers: Deep Dive

These are the fundamental building blocks that enable Arista routers to deliver high-performance, scalable, and programmable routing solutions:

• Arista Extensible Operating System (EOS): The heart of Arista routers, EOS is a Linux-based, modular network OS designed for high availability and programmability. It provides a consistent software image across all devices and supports automation via open APIs.
• Merchant Silicon Chipsets: Arista routers leverage advanced merchant silicon to provide wire-speed packet forwarding and deep packet inspection, enabling low-latency and high-throughput routing.
• Routing Protocol Engines: Support for industry-standard protocols such as BGP, OSPF, IS-IS, EVPN, and Segment Routing ensures interoperability and flexible routing architectures.
• Programmability & Automation Frameworks: Features like eAPI, gRPC, and native Python scripting empower network operators to automate configuration, monitoring, and troubleshooting tasks.
• Telemetry and Analytics Modules: Real-time streaming telemetry, event monitoring, and network analytics help operators gain deep visibility into the network state and performance.
• Hardware Platforms and Modular Line Cards: Arista routers come in various chassis and fixed-form factor models, with modular line cards available for expansion to support growing network demands.

Properly deploying an Arista router requires several key prerequisites. Use this checklist and step-by-step approach to ensure a smooth and secure deployment:

1. Hardware Requirements:
   • For physical routers: Confirm supported Arista platforms (e.g., 7500R, 7280R, 7800R series).
   • For virtual routers (CloudEOS/vEOS): Confirm x86 server with minimum requirements:
     • 4 CPU cores (2.4 GHz or higher)
     • 16 GB RAM or more
     • Intel VT-d support (for virtualization)
     • Supported NICs (e.g., Intel X710, X520, E810)
2. Software Requirements:
   • EOS version 4.20 or newer
   • TerminAttr agent 1.19.5 or newer (for telemetry/CloudVision integration)
   • Compatible hypervisor, if virtualized (KVM, VMware ESXi, etc.)
3. Network Requirements:
   • Management network access (for out-of-band management)
   • Appropriate IP addressing and VLAN planning
   • DNS resolution must be operational for management features
   • Cloud connectivity, if deploying CloudEOS/vEOS in public cloud (AWS/Azure/GCP), ensure correct instance type and enhanced networking features
4. Licensing & Accounts:
   • Valid Arista software license and device serial number
   • Bare metal/cloud: Associated billing account for cloud marketplace or provider portal
5. Access & Security:
   • Console or SSH access to the device for initial setup
   • Configured credentials for admin or network operator login
   • Optional: Set up access controls, secure management interfaces, and enable Zero Touch Provisioning for streamlined onboarding

Once these requirements are met, you’re ready to proceed with Arista router installation and configuration.

Follow these step-by-step instructions to perform a basic initial configuration on an Arista router. This sets up local access, management connectivity, and prepares your router for further customization:

1. Cable and Start the Router:
   • Connect the router to the power source and allow it to boot up (this may take 5–10 minutes).
   • Connect a PC to the console port for CLI access.
2. Login for the First Time:
   • When prompted, log in as admin (no password required on first boot).
   • The device will typically start in Zero Touch Provisioning (ZTP) mode.
3. Cancel ZTP (Zero Touch Provisioning) Mode:
   • At the CLI prompt (localhost>), type: zerotouch cancel
   • This will reboot the router. Wait for it to come back online, then log in again as admin.
4. Enter Privilege and Configuration Modes:
   • Type enable to enter privileged EXEC mode.
   • Then, enter global configuration mode: configure
5. Set Admin Password:
   • Set a password for the admin account (replace YOUR_PASSWORD with a secure value):
     username admin secret YOUR_PASSWORD
6. Configure Management Interface:
   • Enter management interface config mode (replace X/X with your management port):
     interface management X/X
   • Assign an IP address (replace IP_ADDRESS/MASK as needed):
     ip address IP_ADDRESS/MASK
7. Set a Default Route (Gateway):
   • Configure the default gateway for external access (replace GATEWAY_IP):
     ip route 0.0.0.0/0 GATEWAY_IP
8. Save the Configuration:
   • Commit your changes so they persist after a reboot:
     copy running-config startup-config
9. Test Management Access:
   • From a host on the management network, connect via SSH:
     ssh admin@IP_ADDRESS

This initial setup prepares your Arista router for network integration. For advanced configurations (routing protocols, VLANs, security features), refer to the official Arista documentation.

After configuration, it’s crucial to validate that your Arista router is operating as intended. This ensures network reliability, security, and performance. Use these step-by-step methods to verify your deployment:

1. Physical and Interface Validation:
   • Confirm all cables are securely connected and interfaces are up.
   • From the CLI, check interface status:
     show interfaces status
   • Ensure link lights and speed/duplex negotiation are correct.
2. Check Running Configuration:
   • Confirm your settings are correct and persistent:
     show running-config
   • Verify any protocol, routing, or ACL lines are present as expected.
3. Management Connectivity:
   • Test SSH or console access from your management device:
   • ssh admin@<router_ip>
4. Protocol & Routing Verification:
   • For BGP/OSPF/IS-IS, check protocol status:
     show ip bgp summary
show ip ospf neighbor
   • Ensure neighbor relationships are established.
   • Validate routing tables:
     show ip route
5. Testing Packet Forwarding:
   • From the router, ping a known reachable IP:
     ping <remote_ip>
   • If using VRFs, ensure you specify the source VRF in the command (e.g., ping vrf <vrf-name> <remote_ip>).
6. Validate Network State with Automation (AVD):
   • If using Arista Validated Designs (AVD), leverage eos_validate_state for automated validation:
     ansible-playbook validate.yml
   • This tests hundreds of network variables and generates a report of the device’s operational state, matching actual state against your intended configuration.
7. Review Validation Reports:
   • Examine generated validation reports (CSV or Markdown) for pass/fail status, detailed test categories, and troubleshooting hints.
8. Advanced Checks (Optional):
   • Validate logs for errors or warnings:
     show logging
   • Confirm security policies, user access, and AAA configuration are correct for your environment.

A combination of manual show commands and automated validation (via AVD/Ansible) gives high confidence your Arista router is functional, secure, and ready for production use.

Network issues can arise at any stage of deploying or managing Arista routers. This checklist covers proven troubleshooting steps—start from the basics and proceed in order, using these common CLI commands and best practices:

1. Check Physical Connections:
   • Verify all network cables and transceivers are securely connected.
   • Confirm port LEDs indicate link status ("up").
   • For problems at Layer 1 (physical layer), validate port status:
     show interfaces status
2. Validate Interface Status & Configuration:
   • Inspect interface configuration and address assignment:
   • show running-config interface EthernetX
show interfaces EthernetX
   • Check for down/unassigned interfaces, duplex or speed mismatches, or VLAN errors.
   • Use show mac address-table to confirm address learning on L2 ports[6][5].
3. Test Connectivity:
   • Ping the router itself, gateway, and other devices:
   • ping <destination_ip>
traceroute <destination_ip>
4. Verify Routing & Protocols:
   • Ensure routing protocols are running and peerings are correct:
   • show ip route
show ip bgp summary
show ip ospf neighbor
   • Check for missing routes and peer neighbors; confirm prefix advertisements and policy matches.
5. Analyze Logs and Events:
   • View recent logs for errors or warnings:
   • show logging
   • Use show event-handler to inspect automation triggers, if configured[7].
6. Monitor Performance & Environment:
   • Check CPU/resource utilization:
   • show processes top once
   • Inspect environmental status (temperature, power):
     show environment all
7. Leverage Real-Time Monitoring & Tools:
   • For ongoing issues, use watch diff with show commands:
     watch diff show interfaces
   • For advanced packet inspection, utilize tcpdump or flow tracing features.
8. Common Problem Scenarios:
   • Traffic Not Passing: Check VLAN configuration, spanning-tree settings, MAC learning, and port states.
   • Intermittent Connectivity: Validate link stability, check for interface errors, and review protocol neighbor states.
   • Config Drift or Unexpected Behavior: Use show config checkpoint to see recent config changes.
9. Use Support Resources:
   • If hardware faults or bugs are suspected:
   • show version (to collect model/EOS version for support)
   • Consult Arista’s TAC and community forums with logs and configs for further assistance.

Apply changes one at a time and retest after each action. Document commands and findings for efficient troubleshooting and escalation.