Overview
Cisco and Arista are two of the most widely deployed enterprise networking vendors. Cisco IOS-XE powers the ISR, ASR, and Catalyst 9000 product lines, while Arista EOS (Extensible Operating System) runs on the 7000 series data centre and campus switches. This article compares both platforms across CLI syntax, VLAN configuration, routing protocols, high availability, automation, and hardware architecture — giving network engineers a practical reference for working with either or both platforms in the same environment.
Operating System Architecture
The fundamental difference between Cisco IOS-XE and Arista EOS lies in their operating system design. IOS-XE runs a Linux-based kernel with IOS as a daemon, whereas Arista EOS is a fully native Linux OS where the networking stack runs as user-space processes. This architectural distinction affects stability, upgrade behaviour, and programmability.
- Cisco IOS-XE — IOS daemon runs on top of Linux kernel; ISSU support varies by platform; monolithic control plane
- Arista EOS — fully Linux-based; all processes (BGP, STP, LLDP) run as separate Linux daemons; control plane and data plane are fully decoupled; ISSU supported on most platforms
- Configuration model — Both use a running-config / startup-config model with write memory to persist
- Shell access — Arista EOS provides a full Linux bash shell via bash command; Cisco IOS-XE provides a limited guestshell via guestshell
CLI Syntax Comparison
Arista EOS CLI is intentionally modelled after Cisco IOS, making it familiar to Cisco-trained engineers. However, there are meaningful differences in command naming, interface notation, and mode navigation.
Basic Navigation
! Cisco IOS-XE
Router# show running-config
Router# configure terminal
Router(config)# interface GigabitEthernet0/0/0
Router(config-if)# end
! Arista EOS
sw-infrarunbook-01# show running-config
sw-infrarunbook-01# configure terminal
sw-infrarunbook-01(config)# interface Ethernet1
sw-infrarunbook-01(config-if-Et1)# end
Key difference: Arista uses Ethernet<n> for physical ports instead of Cisco's GigabitEthernet, TenGigabitEthernet, or HundredGigE notation. Arista also uses simplified prompt labels (Et1, Vl10, Po1) instead of full interface names.
Interface Naming
- Cisco: GigabitEthernet0/0/1, TenGigabitEthernet1/0/1, HundredGigE1/0/1
- Arista: Ethernet1, Ethernet49, Ethernet1/1 (modular chassis)
- Cisco LAG: Port-channel1
- Arista LAG: Port-Channel1
- Cisco SVI: interface Vlan10
- Arista SVI: interface Vlan10 (identical)
- Cisco loopback: interface Loopback0
- Arista loopback: interface Loopback0 (identical)
VLAN Configuration Comparison
VLAN Creation
! Cisco IOS-XE
sw-infrarunbook-01(config)# vlan 10
sw-infrarunbook-01(config-vlan)# name infrarunbook-mgmt
! Arista EOS
sw-infrarunbook-01(config)# vlan 10
sw-infrarunbook-01(config-vlan-10)# name infrarunbook-mgmt
Access Port
! Cisco IOS-XE
sw-infrarunbook-01(config)# interface GigabitEthernet1/0/1
sw-infrarunbook-01(config-if)# switchport mode access
sw-infrarunbook-01(config-if)# switchport access vlan 20
sw-infrarunbook-01(config-if)# spanning-tree portfast
! Arista EOS
sw-infrarunbook-01(config)# interface Ethernet1
sw-infrarunbook-01(config-if-Et1)# switchport mode access
sw-infrarunbook-01(config-if-Et1)# switchport access vlan 20
sw-infrarunbook-01(config-if-Et1)# spanning-tree portfast
Trunk Port
! Cisco IOS-XE
sw-infrarunbook-01(config)# interface GigabitEthernet1/0/49
sw-infrarunbook-01(config-if)# switchport mode trunk
sw-infrarunbook-01(config-if)# switchport trunk allowed vlan 10,20,30,40
sw-infrarunbook-01(config-if)# switchport trunk native vlan 999
! Arista EOS
sw-infrarunbook-01(config)# interface Ethernet49
sw-infrarunbook-01(config-if-Et49)# switchport mode trunk
sw-infrarunbook-01(config-if-Et49)# switchport trunk allowed vlan 10,20,30,40
sw-infrarunbook-01(config-if-Et49)# switchport trunk native vlan 999
Key VLAN Differences
- DTP — Cisco IOS-XE supports DTP (dynamic trunk negotiation); Arista EOS does not — mode must be configured explicitly
- VTP — Cisco IOS-XE supports VTP v1/v2/v3; Arista EOS does not support VTP — VLANs are managed per-switch or via CloudVision
- vlan.dat — Cisco IOS stores VLAN database in a separate vlan.dat file; Arista EOS stores it in the running-config
- ISL — Cisco legacy ISL trunking is not supported on Catalyst 9000 or any Arista platform
Routing Protocol Comparison
OSPF
! Cisco IOS-XE
Router(config)# router ospf 1
Router(config-router)# router-id 10.0.0.1
Router(config-router)# network 10.10.10.0 0.0.0.255 area 0
! Arista EOS
sw-infrarunbook-01(config)# router ospf 1
sw-infrarunbook-01(config-router-ospf)# router-id 10.0.0.1
sw-infrarunbook-01(config-router-ospf)# network 10.10.10.0/24 area 0.0.0.0
Key difference: Arista uses CIDR notation (/24) for OSPF network statements rather than Cisco's wildcard mask (0.0.0.255). This is a common CLI tripping point for engineers migrating between platforms.
BGP
! Cisco IOS-XE
Router(config)# router bgp 65001
Router(config-router)# bgp router-id 10.0.0.1
Router(config-router)# neighbor 203.0.113.1 remote-as 65002
Router(config-router)# address-family ipv4 unicast
Router(config-router-af)# neighbor 203.0.113.1 activate
! Arista EOS
sw-infrarunbook-01(config)# router bgp 65001
sw-infrarunbook-01(config-router-bgp)# router-id 10.0.0.1
sw-infrarunbook-01(config-router-bgp)# neighbor 203.0.113.1 remote-as 65002
sw-infrarunbook-01(config-router-bgp)# address-family ipv4
sw-infrarunbook-01(config-router-bgp-af)# neighbor 203.0.113.1 activate
EIGRP
! Cisco IOS-XE (Named EIGRP)
Router(config)# router eigrp INFRARUNBOOK
Router(config-router)# address-family ipv4 unicast autonomous-system 100
Router(config-router-af)# network 10.10.10.0 0.0.0.255
! Arista EOS — EIGRP is NOT supported
! Arista supports: OSPF, IS-IS, BGP, RIP, and static routing only
Important: Arista EOS does not support EIGRP. Environments running EIGRP on Cisco must migrate to OSPF or BGP before introducing Arista switches as replacements.
High Availability Comparison
First-Hop Redundancy Protocols
- Cisco IOS-XE — supports HSRP v1/v2, VRRP v2/v3, GLBP
- Arista EOS — supports VRRP v2/v3; does not support HSRP or GLBP
VRRP on Arista EOS
sw-infrarunbook-01(config)# interface Vlan10
sw-infrarunbook-01(config-if-Vl10)# ip address 10.10.10.2/24
sw-infrarunbook-01(config-if-Vl10)# vrrp 10 ip 10.10.10.1
sw-infrarunbook-01(config-if-Vl10)# vrrp 10 priority 110
sw-infrarunbook-01(config-if-Vl10)# vrrp 10 preempt
HSRP on Cisco IOS-XE
sw-infrarunbook-01(config)# interface Vlan10
sw-infrarunbook-01(config-if)# ip address 10.10.10.2 255.255.255.0
sw-infrarunbook-01(config-if)# standby 10 ip 10.10.10.1
sw-infrarunbook-01(config-if)# standby 10 priority 110
sw-infrarunbook-01(config-if)# standby 10 preempt
In-Service Software Upgrade (ISSU)
- Cisco IOS-XE — ISSU supported on select platforms (ASR 1000, Catalyst 9500); requires dual supervisor
- Arista EOS — ISSU supported across all EOS platforms; control plane restarts while data plane continues forwarding (hitless upgrade on most platforms)
Link Aggregation
LACP Configuration
! Cisco IOS-XE
sw-infrarunbook-01(config)# interface GigabitEthernet1/0/1
sw-infrarunbook-01(config-if)# channel-group 1 mode active
sw-infrarunbook-01(config)# interface Port-channel1
sw-infrarunbook-01(config-if)# switchport mode trunk
! Arista EOS
sw-infrarunbook-01(config)# interface Ethernet1
sw-infrarunbook-01(config-if-Et1)# channel-group 1 mode active
sw-infrarunbook-01(config)# interface Port-Channel1
sw-infrarunbook-01(config-if-Po1)# switchport mode trunk
Arista also supports MLAG (Multi-Chassis LAG) — a proprietary active-active LAG across two Arista switches using a peer-link. This is equivalent to Cisco's VSS or StackWise Virtual on Catalyst 9000 platforms.
Automation and Programmability
Arista EOS Automation Features
- eAPI — RESTful HTTP/HTTPS API available on all EOS platforms; supports JSON and text output for any CLI command
- OpenConfig — full OpenConfig model support with gNMI/gNOI
- Ansible — native arista.eos collection in Ansible Galaxy
- Python SDK — pyeapi and the built-in EOS SDK (eAPI Python library)
- CloudVision (CVP) — Arista centralised management, telemetry, and ZTP platform
- ZTP — Zero Touch Provisioning built into EOS bootloader
Cisco IOS-XE Automation Features
- RESTCONF / NETCONF — standard protocol support on IOS-XE 16.6+
- Cisco DNA Center — GUI-based centralised management and automation
- Ansible — cisco.ios collection in Ansible Galaxy
- Python guestshell — limited Python execution environment on IOS-XE
- EEM (Embedded Event Manager) — Tcl/Python scripting for event-driven automation
eAPI Example — Arista EOS
# Query Arista switch via eAPI (curl)
curl -s -u infrarunbook-admin:password -X POST https://10.10.10.1/command-api -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"runCmds","params":{"version":1,"cmds":["show vlan brief"]},"id":1}'
Spanning Tree
- Both platforms support STP, RSTP, MSTP (802.1s), and Rapid PVST+
- Cisco IOS-XE — defaults to PVST+ (per-VLAN STP); Rapid PVST+ is recommended
- Arista EOS — defaults to RSTP (802.1w); MSTP and Rapid PVST+ are also supported
- BPDU Guard, BPDU Filter, PortFast — available on both platforms with identical CLI syntax
- Loop Guard, Root Guard — available on both platforms
Licensing
- Cisco IOS-XE — DNA Advantage/Essentials licensing tiers; many features (SD-Access, telemetry, advanced routing) require DNA Advantage; perpetual and subscription models
- Arista EOS — base EOS is fully featured with no per-feature licensing for routing protocols, VXLAN, or MLAG; CloudVision (CVP) and certain monitoring features are licensed separately
When to Choose Cisco IOS-XE
- Existing Cisco-heavy infrastructure with Cisco DNA Center deployments
- Environments requiring EIGRP, HSRP, GLBP, or VTP
- Campus access-layer deployments with Catalyst 9000 PoE switches
- Teams with deep Cisco IOS expertise and Cisco TAC support contracts
- SD-Access fabric deployments (Cisco proprietary)
When to Choose Arista EOS
- Data centre leaf-spine deployments requiring high-density 100G/400G ports
- Environments prioritising open standards (OpenConfig, gNMI) and API-first automation
- Teams using Ansible, Terraform, or Python for network automation
- High-frequency trading or latency-sensitive workloads (Arista's ultra-low latency platforms)
- Environments wanting full-featured EOS without per-feature licensing costs
Frequently Asked Questions
Does Arista EOS CLI work the same as Cisco IOS?
Arista EOS CLI is intentionally modelled after Cisco IOS, so most basic commands (show, configure terminal, interface, ip address, write memory) are identical. Key differences include interface naming (Ethernet1 vs GigabitEthernet0/0/1), OSPF network statement syntax (CIDR vs wildcard), and the absence of DTP, VTP, EIGRP, and HSRP on Arista.
Does Arista EOS support EIGRP?
No. Arista EOS does not support EIGRP, which is a Cisco proprietary protocol. Environments running EIGRP on Cisco must redistribute into OSPF or BGP at the boundary with Arista switches, or migrate the routing domain to OSPF or BGP entirely.
Can Cisco and Arista switches trunk together?
Yes. Both platforms support IEEE 802.1Q trunking, so they interoperate over 802.1Q trunk links. VLAN IDs, native VLAN, and allowed VLAN lists must be configured consistently on both ends. DTP negotiation from the Cisco side will not produce a trunk on Arista — the Arista port must be explicitly set to trunk mode.
Does Arista support HSRP?
No. Arista EOS supports VRRP v2 and v3 but not HSRP or GLBP. In mixed Cisco/Arista environments where Cisco switches run HSRP, the Arista switches must be configured with VRRP on a different set of SVIs, or the first-hop redundancy must be unified on one platform.
Which platform has better automation support?
Both platforms are highly automatable, but Arista EOS has a slight edge in API-first design: eAPI is available by default on all EOS platforms and returns JSON natively for any CLI command. Cisco IOS-XE requires NETCONF/RESTCONF configuration and YANG model knowledge. Both support Ansible with mature collections (arista.eos and cisco.ios).
Is Arista EOS open source?
Arista EOS is a proprietary operating system built on a Linux kernel. The Linux userspace components are open source per their respective licenses, but EOS itself and the networking daemons are proprietary. Arista does publish EOS extensions and the eAPI SDK as open source tools.
Does Arista support VTP?
No. Arista EOS does not support VTP (VLAN Trunking Protocol). VLAN databases must be configured per-switch or managed centrally via Arista CloudVision (CVP) or automation tools such as Ansible, Terraform, or NAPALM.
What are the main advantages of Arista EOS over Cisco IOS-XE?
Arista EOS advantages include: native Linux OS with full bash access, eAPI for JSON-based automation without a separate controller, hitless ISSU across all platforms, open standards support (OpenConfig, gNMI), full feature set without per-feature licensing, and ultra-low latency hardware options for data centre and HFT workloads.
What routing protocols does Arista EOS support?
Arista EOS supports OSPFv2, OSPFv3, BGP-4 (eBGP and iBGP), IS-IS, RIPv2, RIPng, PIM, IGMP, BFD, and static routing. It does not support EIGRP. All routing protocols are included in base EOS without additional licensing.
How do I migrate from Cisco HSRP to Arista VRRP?
Deploy Arista switches with VRRP configured on the same subnets where Cisco switches run HSRP. Because HSRP and VRRP are not compatible protocols, the transition requires a maintenance window to cut over gateway IPs. Use a temporary static route or redistribute routes to maintain reachability during the migration. After cutting over, update client default gateways if the virtual IP changes.
Can I run Arista EOS in a virtual machine for lab purposes?
Yes. Arista provides vEOS-lab (a virtual Arista EOS image) and cEOS-lab (a containerised EOS image) for lab and testing purposes. Both are available for download from the Arista support portal with a free registration and run on standard x86 hypervisors or container engines.
Which platform is better for data centre leaf-spine?
Arista EOS is the dominant choice for data centre leaf-spine deployments due to its high-density 100G/400G port counts, MLAG for active-active LAG, native VXLAN/EVPN support, ultra-low latency, and eAPI automation. Cisco Nexus (NX-OS) is the comparable Cisco offering for data centre — Catalyst IOS-XE is primarily a campus and WAN platform.
