Key Technical Specifications
| Parameter | Specification |
|---|---|
| Full Model | A4H124-24TX |
| OEM Part Reference | P0973JM (commonly listed) |
| Manufacturer | Enterasys Networks / Extreme Networks |
| Product Family | A4 Series stackable managed switches |
| Fixed Ports | 24× 10/100BASE-TX RJ45 |
| Uplink Slots | 2× SFP (hot-pluggable, model-dependent) |
| Stacking | Up to 8 switches per stack group |
| Switching Mode | Store-and-forward |
| MAC Address Table | Up to 16,000 entries (A4 Series) |
| VLAN Support | IEEE 802.1Q VLANs |
| QoS | 802.1p priority queuing |
| Management | Web UI, CLI, SNMP, Telnet |
| Redundant Power | External RPS: STK-RPS-150PS / STK-RPS-500PS |
| Mounting | 1U 19-inch rack-mount or desktop |
| Power Input | Verify on nameplate; some listings cite 100–240 V AC, but confirm before wiring |
| Status | Obsolete; verify firmware revision and port count before purchase |
Product Introduction
The A4H124-24TX is one of those switches you find tucked into a control-room rack, a wiring closet, or a plant LAN where nobody has touched the config since 2014. It is a 24-port 10/100 managed switch with two SFP uplink slots and stackable architecture. Not a gigabit copper switch. Not a DCS controller. Not a Foxboro I/A module — despite what some surplus listings claim.Engineers keep these in service because they are simple, predictable, and easy to stack. You get 24 ports of 10/100, two SFP uplinks for fiber backhaul, and a management set that covers VLANs, QoS, SNMP, and basic security. The fan noise is low enough for office-adjacent rooms, and the external RPS option means a single power-supply failure does not have to take down the whole stack. Just do not expect modern PoE budgets, web GUI polish, or current security patches. This is legacy Enterasys/Extreme hardware, and it should be treated as such.
Quality SOP & Tech Pitfalls
The Lab Report (SOP)
We begin with a visual inspection: nameplate, P0973JM marking, serial number, revision, RJ45 pins, SFP cage condition, power connector, and any signs of rework. Then it goes onto a test bench for live power-up, port-by-port link testing, SFP uplink verification, stacking-cable validation, VLAN/QoS sanity checks, and SNMP/Web-UI accessibility. We log the firmware revision, verify MAC learning, and confirm the RPS connector is intact. Final steps are insulation/continuity checks where appropriate, anti-static bagging, and reinforced packing. Test photos and a basic test report can be provided.The Engineer’s Warning (Pitfalls)
- Do not confuse this with a gigabit copper switch. The A4H124-24TX is a 24× 10/100BASE-TX unit with SFP uplinks. If your plant floor now expects 10/100/1000 on every port, this is not the right replacement.
- Firmware revision matters. Older Enterasys firmware may not match your existing stack master, and mismatched revisions can cause stacking instability or missing features.
- Stacking cables are not generic Ethernet cables. Use the correct Enterasys/Extreme stacking modules and cables. Wrong cabling breaks the stack ring and can isolate switches.
- Verify the power supply before energizing. Some listings are vague. Read the actual nameplate. Do not assume 100–240 V AC without confirmation.
- Surplus listings sometimes mislabel this as a Foxboro/DCS module. It is not. It is an Ethernet switch.
Installation & Configuration Guide
- Pre-Installation
- Photograph the existing switch: nameplate, firmware version, port map, VLAN assignments, IP address, and stacking IDs.
- Verify whether it is part of an active stack.
- Confirm power type and voltage from the nameplate.
- Removal
- ⚠️ If the switch is stacked, confirm stack topology and management IP before removal.
- Label all RJ45 and SFP connections.
- Disconnect power and stacking cables safely.
- Remove the unit and place it in an anti-static bag.
- Installation
- Match firmware revision to the existing stack if possible. This prevents most stacking and feature mismatches.
- Mount the switch in the rack or desktop location.
- Reconnect RJ45 ports and SFP uplinks exactly as labeled.
- Reconnect stacking cables in the correct order.
- Power-On & Testing
- Verify power input and LED status.
- Confirm stack membership and switch ID.
- Check VLAN, QoS, SNMP, and port security settings.
- Test SFP uplinks and verify link stability.
- Run a controlled traffic test before returning the segment to full production.
Compatible Replacement Models
| Replacement | Compatibility | Notes |
|---|---|---|
| Enterasys/Extreme A4H124-24TX (P0973JM) | ✅ Drop-in | Same model. Match firmware revision and stacking configuration. |
| Enterasys/Extreme A4H124-24 | ⚠️ Engineering review | Same A4 Series family, but verify port type, SFP support, firmware, and stack compatibility. |
| Extreme Networks A4 Series replacement | ⚠️ Firmware/config migration | Modern Extreme A4 replacements may require firmware alignment and configuration rebuild. |
| Any non-A4 gigabit switch | ❌ Not a direct swap | Would require VLAN/QoS reconfiguration, IP changes, and possible stack redesign. |
Frequently Asked Questions (FAQ)
Is the A4H124-24TX a gigabit switch?
No. It is a 24-port 10/100BASE-TX switch with two SFP uplink slots. The uplinks can be gigabit depending on the SFP, but the 24 copper ports are 10/100.Can I stack it with other A4 switches?
Yes. The A4 Series supports stacking up to eight units per stack group, using the correct stacking modules and cables.Does it support PoE?
Not as a standard feature on the base A4H124-24TX. PoE variants exist in the A4 family, such as the A4H124-24P, but you must verify the exact model and nameplate.Can I use it as a direct replacement for an A4H124-24?
Usually yes, but confirm firmware revision, SFP compatibility, stacking ID, and port configuration before deploying it into an active stack.Is this a Foxboro or DCS module?
No. Some surplus listings mislabel it. The A4H124-24TX is an Enterasys/Extreme Ethernet switch, not a Foxboro I/A Series controller or I/O module.What should I send before ordering?
A photo of the nameplate, the current firmware version, the stack topology, the IP address scheme, and the SFP types in use. That avoids buying the wrong revision.Can I run it standalone?
Yes. It works as a standalone managed switch or as part of a stack. If you are replacing a failed unit in a stack, match the firmware and switch ID carefully.
