Key Technical Specifications
| Parameter | Detail |
|---|---|
| Manufacturer | Enterasys Networks |
| Model | A4H124-24TX |
| Series | A4 Series Stackable Fast Ethernet Switch |
| Copper Ports | 24 × 10/100BASE-TX RJ45 |
| SFP Ports | 2 × SFP (100BASE-FX/1000BASE-X, optics sold separately) |
| Stacking/Uplink Ports | 2 × 10/100/1000BASE-T RJ45 |
| Switching Capacity | 12.8 Gbps per switch; 102.4 Gbps stacked |
| Forwarding Rate | 9.5 Mpps per switch; 76.2 Mpps stacked |
| MAC Address Table | 8K entries (verify with OEM datasheet) |
| Management | CLI, WebView (HTTP), SNMP, Telnet, Console (DB9) |
| VLAN Support | IEEE 802.1Q VLANs |
| QoS | IEEE 802.1p priority queuing |
| Redundant Power | External RPS via STK-RPS-150PS |
| Standards | IEEE 802.3, 802.3u, 802.3ab, 802.3ad, 802.3z, 802.3x |
| Safety | UL 60950-1, CSA 22.1 60950, EN 60950-1, IEC 60950-1 |
| Cooling | Fan-cooled (higher acoustic level than fanless FX variants) |
| Mounting | 19-inch rack-mountable, 1U |
| Status | Discontinued / EOL |
Product Introduction
The Enterasys A4H124-24TX belongs to the old A4 stackable Fast Ethernet family — the generation of switches that showed up in plant offices, control rooms, and light industrial racks long before “smart managed switch” became a marketing slogan. It gives you 24 copper ports, two SFP slots for fiber uplinks, and two gigabit stacking/uplink ports, which was a solid layout for a control-room access switch when Gigabit-to-the-desktop was still optional.Engineers kept these boxes because they were simple to stack, easy to manage through CLI or WebView, and predictable once configured. The 12.8 Gbps switching capacity and 9.5 Mpps forwarding rate are not impressive by modern data-center standards, but they are more than adequate for HMI stations, engineering workstations, printer segments, and non-real-time plant LAN traffic. The real limitation today is availability. This is a discontinued Enterasys product, so firmware updates, RPS units, and SFP compatibility should be checked before committing it to a live system.
Quality SOP & Tech Pitfalls
The Lab Report (SOP)
- Visual and counterfeit check: verify Enterasys branding, model label A4H124-24TX, serial number, and MAC address label. Check for replaced feet, mismatched screws, or reprinted labels.
- Port inspection: inspect all 24 RJ45 ports, 2 SFP cages, 2 gigabit stacking/uplink ports, console DB9, and power connector for bent pins, corrosion, or loose latches.
- Power-up test: apply rated AC power and confirm normal POST behavior, fan operation, and LED status.
- Console access: connect to the DB9 console port and verify CLI access, boot loader response, and firmware version.
- Port functional check: verify link/activity on a sample of copper ports and confirm SFP cage detection.
- Configuration reset check: confirm the unit can be reset to factory defaults and reconfigured via CLI or WebView.
- Firmware logging: record firmware/ROM versions before packing.
- ESD-safe packing: anti-static bag, foam support, and rigid outer box.
The Engineer’s Warning (Pitfalls)
Do not trust third-party listings that call this a 24-port Gigabit switch. The A4H124-24TX is a 24 × 10/100 switch with separate gigabit stacking/uplink ports. If your design assumes Gigabit copper on all 24 ports, this unit will not work.The second common failure is buying an A4 switch without confirming RPS compatibility. The A4 family supports external redundant power through the STK-RPS-150PS, but surplus units rarely include it. If this switch sits in a single power path feeding HMIs or historians, plan for an external UPS or redundant feed instead of assuming RPS availability.
Installation & Configuration Guide
1. Pre-Installation ⚠️
- Confirm whether this switch carries any safety-related or trip-related traffic. If it does, treat the replacement as a controlled change.
- Back up the current switch configuration if the unit is still accessible.
- Photograph port mappings, VLAN assignments, uplink connections, and rack power feeds.
- Verify replacement model is A4H124-24TX and not A4H124-24P, A4H124-48, or A4H124-24FX.
2. Removal
- Label all Ethernet cables by port number.
- Label uplink, stacking, and console cables.
- Disconnect AC power after confirming the change window.
- Remove rack ears and slide the unit from the rack.
3. Installation
- Mount the replacement A4H124-24TX in the same rack position.
- Reconnect cables according to the port map.
- Verify SFP modules match the original type and wavelength if fiber uplinks are used.
- Confirm AC power rating and plug type before energizing.
4. Power-On & Testing
- Apply power and verify normal fan and LED behavior.
- Access the console port and confirm firmware loads.
- Restore VLANs, trunk ports, management IP, SNMP community strings, and ACLs from backup.
- Verify uplink connectivity, stacking status if applicable, and port-by-port link status.
- Monitor for CRC errors or duplex mismatches on the 10/100 ports before closing the work order.
Compatible Replacement Models
- ✅ Enterasys A4H124-24TX (same model): Direct replacement if port mapping, VLANs, and firmware capabilities match. Confirm SFP and RPS availability.
- ⚠️ Enterasys A4H124-24 / A4H124-24P: Same 24-port Fast Ethernet platform, but the -24P adds 802.3af PoE. Configuration may need adjustment for PoE, VLANs, or stacking. Expect 1–2 hours of engineering time for verification.
- ⚠️ Extreme Networks A4 series replacements: After Enterasys was acquired by Extreme Networks, some A4 models continued under Extreme branding. Firmware, CLI syntax, and SFP compatibility should be verified against the current OEM documentation.
- ❌ A4H124-24FX, A4H124-48, A4H124-48P: Not direct drop-in replacements. The FX variant uses fiber ports, and the 48-port models change rack space, power, and port count. Use only with a full redesign.
Frequently Asked Questions (FAQ)
Is the A4H124-24TX a Gigabit switch?
No. It is a 24-port 10/100 Fast Ethernet switch with two additional 10/100/1000 stacking/uplink ports and two SFP ports. Some reseller listings claim 10/100/1000 on all 24 ports, but that does not match the OEM A4 datasheet.Can I still manage this switch today?
Yes. It supports CLI through a DB9 console port, WebView HTTP management, SNMP, and Telnet. For modern networks, disable Telnet if possible and restrict SNMP access.Does it support PoE?
The A4H124-24TX does not include PoE. The A4H124-24P variant adds 802.3af PoE on the 24 copper ports. Do not assume PoE capability unless the model suffix is -24P.Can I stack it with other A4 switches?
Yes. The A4 series supports stacking through the two 10/100/1000 stacking/uplink ports using standard Cat5 or better cabling. Verify firmware compatibility before mixing different A4 models in a stack.Is redundant power available?
The A4 series supports an external redundant power supply, typically the STK-RPS-150PS. These RPS units are hard to find today, so plan for UPS protection or dual AC feeds instead.Is this unit still supported by the OEM?
No. Enterasys was acquired by Extreme Networks, and the A4H124-24TX is a discontinued product. Support depends on existing documentation, saved configurations, and available surplus spares.What should I back up before replacing it?
Save the running configuration, VLAN table, port-to-device map, management IP, SNMP settings, firmware version, and any stacking configuration. On an old plant switch, that port map is often the only record of what connects to what.
