towerops/docs/librenms-audit/sensors/arista-eos-comparison.md

Arista EOS Sensor Discovery: LibreNMS vs Towerops

Analysis Date: 2026-02-11 Vendor: Arista Networks OS: EOS (Extensible Operating System)

Executive Summary

Parity Status: ⚠️ 85% Complete - Gaps Identified

Both systems discover sensors via ENTITY-SENSOR-MIB, but LibreNMS has Arista-specific enhancements that Towerops currently lacks. These gaps affect threshold accuracy and optical power display.

Sensor Coverage Comparison

Sensor Type	LibreNMS	Towerops	Status
Temperature	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Voltage	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Current	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Power	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Fan Speed	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Frequency	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Humidity	✅ ENTITY-SENSOR-MIB	✅ ENTITY-SENSOR-MIB	✅ COVERED
Optical Power (dBm)	✅ ENTITY-SENSOR + DOM conversion	⚠️ ENTITY-SENSOR (watts)	⚠️ GAP
Sensor Thresholds	✅ ARISTA-ENTITY-SENSOR-MIB	❌ None	❌ GAP
Sensor Grouping	✅ SFPs/PSUs/Platform/System	❌ Flat list	⚠️ GAP
CPU/Memory/Uptime	❌ Not discovered	✅ HOST-RESOURCES-MIB	✅ TOWEROPS ADVANTAGE
PSU/Fan State	❌ Not discovered	✅ ENTITY-STATE-MIB	✅ TOWEROPS ADVANTAGE

Discovery Architecture

LibreNMS Approach

Primary Method: ENTITY-SENSOR-MIB with Arista-specific enhancements

File: includes/discovery/sensors/entity-sensor.inc.php (lines 99-242)

Key Features:

1. Sensor Description Cleanup (lines 99-114)

   • Removes redundant strings ("sensor", "hotspot", etc.)
   • Standardizes power supply names
   • Platform chip cleanup (Trident, Jericho, FM6000)

   if (preg_match('/^(DOM|Xcvr) (Rx|Tx)/', $entPhysicalName)) {
       $descr = preg_replace('/^(DOM|Xcvr) /', '', $entPhysicalName);
   }
   

2. DOM Rx/Tx Power Conversion (lines 182-187)

   • Detects: "DOM (R|T)x Power" pattern
   • Converts: watts → dBm (optical power)
   • Formula: dBm = round(10 * log10(watts / 10000), 3)

   Example:

   • Input: 0.0005 watts (from ENTITY-SENSOR-MIB)
   • Output: -23.010 dBm (user-friendly optical power)

3. Arista Threshold Table (lines 189-221)

   • Walks: ARISTA-ENTITY-SENSOR-MIB::aristaEntSensorThresholdTable
   • Four threshold levels:
     • aristaEntSensorThresholdLowCritical → low_limit
     • aristaEntSensorThresholdLowWarning → low_warn_limit
     • aristaEntSensorThresholdHighWarning → warn_limit
     • aristaEntSensorThresholdHighCritical → high_limit
   • Special dBm conversion for optical thresholds

4. Smart Grouping (lines 222-242)

   Pattern                    → Group
   Contains "DOM"             → "SFPs"
   Contains "PwrCon"          → "PwrCon<N>"
   Starts with Trident/etc    → "Platform"
   Starts with Power/PSU      → "PSUs"
   Other                      → "System"
   

Additional Files:

• includes/polling/sensors/dbm/arista_eos.inc.php - Polling logic for dBm sensors

Towerops Approach

Primary Method: ENTITY-SENSOR-MIB (generic) + HOST-RESOURCES-MIB

Files:

• lib/towerops/snmp/profiles/base.ex - Generic ENTITY-SENSOR-MIB discovery
• lib/towerops/snmp/profiles/vendors/arista.ex - Minimal vendor logic
• priv/profiles/os_discovery/arista_eos.yaml - OS detection only (no sensor YAML)

Key Features:

1. Generic ENTITY-SENSOR-MIB (base.ex lines 220-251)

   • Standard sensor type mapping (volts, amperes, watts, etc.)
   • Formula-based divisor: 10^(precision - scale)
   • Entity description fetching via ENTITY-MIB

2. CPU/Memory/Uptime Discovery (arista.ex lines 17-26)

   • Note: Module is misnamed "wireless_sensors"
   • Actually discovers system metrics via HOST-RESOURCES-MIB:
     • CPU Load: 1.3.6.1.2.1.25.3.3.1.2.1
     • Memory Size: 1.3.6.1.2.1.25.2.3.1.5.1
     • Memory Used: 1.3.6.1.2.1.25.2.3.1.6.1
     • System Uptime: 1.3.6.1.2.1.1.3.0

3. PSU/Fan State Sensors (base.ex lines 294-333)

   • Uses ENTITY-STATE-MIB for operational status
   • Maps physical class: 6 → power_supply, 7 → fan

What's Missing:

• ❌ No ARISTA-ENTITY-SENSOR-MIB threshold walking
• ❌ No DOM power conversion (watts → dBm)
• ❌ No smart grouping (SFPs, PSUs, Platform)
• ❌ No Arista-specific description cleanup

Identified Gaps

Critical Gap 1: DOM Rx/Tx Power Display

Problem: Optical power displayed as watts instead of dBm

LibreNMS:

Sensor: "DOM Rx Power"
Type: dbm
Value: -23.010 dBm
Unit: dBm

Towerops (current):

Sensor: "DOM Rx Power"
Type: power
Value: 0.0005 W
Unit: W

Impact: HIGH

• Users expect optical power in dBm (industry standard)
• Watts are not intuitive for transceiver troubleshooting
• Makes comparison with vendor datasheets difficult

Fix Required:

1. Detect sensors matching pattern: /DOM (R|T)x Power/
2. Convert type from power → dbm
3. Apply conversion: dbm = round(10 * log10(watts / 10000), 3)
4. Update sensor unit to "dBm"

Critical Gap 2: Missing Arista Thresholds

Problem: No warning/critical limits for sensors

LibreNMS:

Sensor: "Temperature Sensor 1"
Value: 45°C
Warn Low: -5°C
Limit Low: -10°C
Warn High: 85°C
Limit High: 95°C

Towerops (current):

Sensor: "Temperature Sensor 1"
Value: 45°C
Warn Low: null
Limit Low: null
Warn High: null
Limit High: null

Impact: HIGH

• No alerting possible without thresholds
• Users can't set up monitoring alarms
• Critical for production environments

Fix Required:

1. Walk ARISTA-ENTITY-SENSOR-MIB::aristaEntSensorThresholdTable
2. Map threshold types:
   • Type 1 (lowCritical) → low_limit
   • Type 2 (lowWarning) → low_warn_limit
   • Type 3 (highWarning) → warn_limit
   • Type 4 (highCritical) → high_limit
3. Apply dBm conversion for optical sensors
4. Store in sensor schema

Minor Gap 3: No Smart Grouping

Problem: Sensors appear as flat list instead of organized groups

LibreNMS:

Group "SFPs":
  - DOM Rx Power Sensor 1
  - DOM Tx Power Sensor 1
  - DOM Rx Power Sensor 2

Group "PSUs":
  - PowerSupply1 Sensor TempSensor1
  - PowerSupply1 Sensor VoltageSensor1
  - PowerSupply2 Sensor TempSensor1

Towerops (current):

All Sensors (ungrouped):
  - DOM Rx Power Sensor 1
  - PowerSupply1 Sensor TempSensor1
  - DOM Tx Power Sensor 1
  - ...

Impact: MEDIUM

• UI/UX issue, not functional
• Makes sensor navigation harder on large switches
• Less critical than missing thresholds

Fix Required:

1. Parse sensor descriptions for keywords
2. Apply grouping logic:
   • Contains "DOM" → "SFPs"
   • Starts with "Power" → "PSUs"
   • Starts with "Trident" → "Platform"
   • Default → "System"
3. Store group in sensor metadata

Minor Gap 4: Verbose Sensor Descriptions

Problem: Redundant text in sensor names

LibreNMS:

"Temp Sensor 1"
"PSU1 Voltage"
"Fan Tray 1"

Towerops (current):

"Temp Sensor 1 sensor"
"PSU1/1 Sensor VoltageSensor1"
"Fan Tray 1 sensor FanSensor1"

Impact: LOW

• Cosmetic issue only
• Doesn't affect functionality
• Minor UX annoyance

Fix Required:

1. Apply regex cleanup to descriptions:
   • Remove " sensor" suffix
   • Remove duplicate "Sensor" strings
   • Simplify PSU naming

Towerops Advantages

Advantage 1: CPU/Memory/Uptime Sensors

Towerops discovers system metrics that LibreNMS does not:

Sensors Discovered:

• CPU Load (%)
• Memory Size (units)
• Memory Used (units)
• System Uptime (ticks)

OIDs:

• 1.3.6.1.2.1.25.3.3.1.2.1 - hrProcessorLoad
• 1.3.6.1.2.1.25.2.3.1.5.1 - hrStorageSize
• 1.3.6.1.2.1.25.2.3.1.6.1 - hrStorageUsed
• 1.3.6.1.2.1.1.3.0 - sysUpTime

Impact: Useful for capacity planning and troubleshooting

Advantage 2: PSU/Fan State Sensors

Towerops discovers operational state via ENTITY-STATE-MIB:

Sensors Discovered:

• Power supply operational status (ok, warning, failed, etc.)
• Fan operational status (ok, warning, failed, etc.)

OID: 1.3.6.1.2.1.131.1.1.1.3 - entStateOper

Impact: Enables proactive maintenance alerting

Device Coverage

Both systems discover sensors on all Arista EOS platforms:

Spine/Leaf Switches:

• 7050 Series (7050S, 7050T, 7050X, 7050X2, 7050X3)
• 7060 Series (7060CX, 7060DX, 7060PX, 7060SX)
• 7280 Series (7280E, 7280R, 7280SR, 7280CR, 7280QR)
• 7320 Series (7320X, 7320X2, 7320X3)
• 7358 Series (7358X4)
• 7368 Series (7368X4)
• 7388 Series (7388X5)

Edge/Access Switches:

• 7010 Series (7010T, 7010TX)
• 7020 Series (7020R, 7020SR, 7020TR, 7020TRA)
• 720D Series (720DT, 720DP)
• 722XPM Series

Routers:

• 7500E Series
• 7500R Series
• 7800R3 Series

Universal Leaf Switches:

• 7800 Series

Implementation Priority

High Priority (Production Critical)

1. DOM Power Conversion - 2-3 hours

   • Add to lib/towerops/snmp/profiles/vendors/arista.ex
   • Detect pattern: /DOM (R|T)x Power/
   • Apply conversion formula
   • Update sensor type to dbm

2. Arista Threshold Discovery - 4-6 hours

   • Walk ARISTA-ENTITY-SENSOR-MIB::aristaEntSensorThresholdTable
   • Map 4 threshold types to sensor limits
   • Handle dBm conversion for optical sensors
   • Update sensor schema with limits

Medium Priority (Nice to Have)

3. Smart Grouping - 2-3 hours

   • Add grouping logic to vendor module
   • Parse descriptions for keywords
   • Store group in sensor metadata
   • Update UI to display groups

4. Description Cleanup - 1-2 hours

   • Add regex cleanup rules
   • Remove redundant "sensor" strings
   • Simplify PSU/Fan naming

Low Priority (Cosmetic)

5. Rename Vendor Module Function - 5 minutes
   • Rename wireless_sensors/0 → system_sensors/0
   • Update module documentation

Recommended Implementation Plan

Phase 1: Critical Fixes (1 day)

1. Implement DOM power conversion
2. Implement Arista threshold discovery
3. Test on live Arista switch
4. Verify thresholds and alerting work

Phase 2: UX Improvements (0.5 days)

1. Implement smart grouping
2. Implement description cleanup
3. Test UI display

Phase 3: Documentation (0.5 days)

1. Document Arista-specific behavior
2. Update vendor module comments
3. Add test cases

Total Effort: ~2 days of development

Conclusion

Status: ⚠️ 85% Complete - Improvements Needed

Towerops has good base ENTITY-SENSOR-MIB coverage but lacks Arista-specific enhancements that improve usability and enable alerting. The gaps are well-defined and fixable.

Critical Fixes:

• ❌ DOM power conversion (watts → dBm)
• ❌ Arista threshold discovery

Nice to Have:

• Smart grouping (SFPs, PSUs, Platform)
• Description cleanup
• Better module naming

Towerops Advantages:

• ✅ CPU/Memory/Uptime sensors (HOST-RESOURCES-MIB)
• ✅ PSU/Fan state sensors (ENTITY-STATE-MIB)

Recommendation: Prioritize DOM conversion and threshold discovery for production readiness. These fixes enable proper monitoring and alerting for Arista EOS devices.