Overview
O-Chain is ORing's proprietary chain redundancy protocol that connects multiple switches in an open-chain topology with a backup link, achieving sub-20 ms fault recovery when any link or switch in the chain fails. Unlike O-Ring — which forms a closed ring — O-Chain is designed for linear network architectures where a fully closed ring is not physically possible, such as multi-building industrial networks or topologies that include a third-party core switch. ORing managed switches ([PRODUCT_MODELS]) support O-Chain alongside O-Ring, but only one protocol can be active per switch at a time. This guide configures O-Chain across three switches: SW1 (Core Switch) and SW2/SW3 (O-Chain members).
Prerequisites
- Applicable models: ORing managed switches ([PRODUCT_MODELS])
- Minimum firmware: [FIRMWARE_VERSION]
- Login level required: Administrator
- O-Ring must be disabled on all three switches before enabling O-Chain
- SW1 Port 9 cable must be disconnected before starting configuration (see Step 1 for the reason)
O-Chain vs O-Ring — key differences
| Feature | O-Ring | O-Chain |
|---|---|---|
| Topology | Closed ring (loop) | Open chain with one backup link |
| Recovery time | < 20 ms | < 20 ms |
| Use case | Single building / single ring | Multi-segment, multi-building, third-party core |
| Can coexist with O-Ring? | — | No — must disable O-Ring first |
| Edge Port setting required? | No | Yes — two outermost chain ends only |
Edge Port — what it means and which ports need it
Edge Port marks a port as the open end of the O-Chain — the point where the chain terminates. Only two ports in the entire chain should have Edge Port = Enable: the two outermost ports at each end of the chain. All intermediate ports connecting switches within the chain must have Edge Port = Disable.
In this three-switch example:
- Edge Port = Enable: SW1 Port 9 and SW2 Port 19 — these are the two open ends of the chain
- Edge Port = Disable: all other O-Chain ports (SW1 Port 10, SW2 Port 20, SW3 Port 19, SW3 Port 20)
Setting Edge Port = Enable on an intermediate port prevents that port from forming a correct O-Chain connection and will cause the redundancy protocol to fail silently.
Test topology — before configuration (Port 9 disconnected)
| Switch | Role | 1st Port | Edge Port | 2nd Port | Edge Port |
|---|---|---|---|---|---|
| SW1 | Core Switch | Port 9 | Enable (backup link end) | Port 10 | Disable |
| SW2 | O-Chain Member | Port 19 | Enable (chain end) | Port 20 | Disable |
| SW3 | O-Chain Member | Port 19 | Disable | Port 20 | Disable |
Part 1 — Preparation: disconnect backup link and disable O-Ring
Step 1 — Disconnect SW1 Port 9 and disable O-Ring on all switches
Before making any configuration changes, physically disconnect the cable from SW1 Port 9. This port will become the backup link after configuration is complete. It must remain disconnected until all three switches have been configured and saved — otherwise a temporary physical loop will form during the transition from O-Ring to O-Chain, causing a broadcast storm.
Next, navigate to [MENU_PATH_OCHAIN] on each switch and disable the O-Ring function. O-Ring and O-Chain cannot run simultaneously on the same switch. The sequence is:
- Disconnect SW1 Port 9 cable
- Disable O-Ring on SW1, SW2, and SW3 (save configuration on each)
- Proceed to configure O-Chain on each switch (Steps 2–4)
- Reconnect SW1 Port 9 only after all three switches are configured (Step 5)
Part 2 — Configure SW1 (Core Switch)
Step 2 — Enable O-Chain on SW1 and set port roles
Navigate to [MENU_PATH_OCHAIN] on SW1. Enable O-Chain and configure the two O-Chain ports:
- 1st port = Port 9, Edge Port = Enable — Port 9 is the backup link at the open end of the chain. Setting Edge Port = Enable tells SW1 that this port is a chain terminus, not an intermediate connection.
- 2nd port = Port 10, Edge Port = Disable — Port 10 connects toward SW2 and is an intermediate link, not a chain end.
Save configuration on SW1
After applying the O-Chain settings, save the configuration. The configuration must be saved before proceeding to SW2 — an unsaved configuration will be lost if the switch reboots during the setup process.
Part 3 — Configure SW2 (O-Chain Member)
Step 3 — Enable O-Chain on SW2 and set port roles
Navigate to [MENU_PATH_OCHAIN] on SW2. Enable O-Chain and configure the two O-Chain ports:
- 1st port = Port 19, Edge Port = Enable — Port 19 connects toward SW1 and is at the open end of the chain facing the backup link. Edge Port = Enable marks this as a chain terminus.
- 2nd port = Port 20, Edge Port = Disable — Port 20 connects toward SW3 and is an intermediate link.
Save the configuration on SW2 after applying these settings.
Part 4 — Configure SW3 (O-Chain Member)
Step 4 — Enable O-Chain on SW3 and set port roles
Navigate to [MENU_PATH_OCHAIN] on SW3. Enable O-Chain and configure the two O-Chain ports:
- 1st port = Port 19, Edge Port = Disable — Port 19 connects toward SW2. This is an intermediate link; SW3 is not at the open end of the chain.
- 2nd port = Port 20, Edge Port = Disable — Port 20 connects toward the next device in the chain. Both ports on SW3 are intermediate connections, so both have Edge Port = Disable.
SW3 has both Edge Ports disabled because it is an intermediate node in the chain — neither of its O-Chain ports is at an open end. Only SW1 Port 9 and SW2 Port 19, which are the two open ends of the entire chain, should have Edge Port = Enable.
Save the configuration on SW3 after applying these settings.
Part 5 — Activate the backup link and verify O-Chain operation
Step 5 — Reconnect SW1 Port 9 to activate the backup link
After all three switches have been configured and saved, reconnect the cable to SW1 Port 9. This port now becomes the backup link (standby link) for the O-Chain.
In normal operation, SW1 Port 9 is in a blocking (standby) state — it does not forward regular traffic. If any link or switch in the O-Chain fails, the O-Chain protocol detects the failure and activates SW1 Port 9 within 20 ms, restoring full network connectivity through the backup path.
Verification checklist
- ✅ SW1 Port 9 link LED is active (cable connected, link up)
- ✅ SW1 Port 9 is in blocking/standby state in the O-Chain status page — it should not be forwarding normal traffic
- ✅ All three switches show O-Chain status as Normal (not Fault)
- ✅ Network connectivity across all three switches is confirmed (ping test from end devices)
- ✅ Fault recovery test: disconnect any intermediate link and verify connectivity restores within 20 ms; reconnect the link and verify the backup returns to standby
Configuration summary
| Switch | Role | O-Ring | O-Chain | 1st Port | Edge | 2nd Port | Edge |
|---|---|---|---|---|---|---|---|
| SW1 | Core Switch | Disabled | Enabled | Port 9 | Enable | Port 10 | Disable |
| SW2 | O-Chain Member | Disabled | Enabled | Port 19 | Enable | Port 20 | Disable |
| SW3 | O-Chain Member | Disabled | Enabled | Port 19 | Disable | Port 20 | Disable |
Troubleshooting common O-Chain issues
O-Chain status shows Fault — backup link not activating after disconnecting a link
Check in this order: (1) verify Edge Port = Enable only on SW1 Port 9 and SW2 Port 19 — all other O-Chain ports must be Disable; setting Edge Port = Enable on an intermediate port is the most common configuration error; (2) confirm O-Ring is disabled on all three switches; (3) verify the O-Chain configuration is saved on all switches — unsaved settings are lost on reboot; (4) confirm SW1 Port 9 cable is connected and the link LED is active; (5) check all O-Chain ports are in a physically active link state.
Network loop / broadcast storm after enabling O-Chain
This occurs when SW1 Port 9 was connected before O-Chain was fully configured on all switches. Immediately disconnect SW1 Port 9 to break the loop. Then verify: (1) O-Ring is disabled on all switches; (2) O-Chain is correctly configured on all switches and saved; (3) reconnect SW1 Port 9 only after steps 1–2 are confirmed. The transition window between disabling O-Ring and enabling O-Chain is when loops can form if the backup link port is connected.
SW3 O-Chain ports not forming — stuck in connecting state
If SW3 O-Chain ports do not form correctly after configuration, verify: (1) both SW3 ports have Edge Port = Disable — SW3 is an intermediate node, not a chain end; (2) the physical cables between SW2 Port 20 → SW3 Port 19 and SW3 Port 20 → the next device are connected and active; (3) SW3 O-Chain is enabled and configuration is saved. Check the O-Chain status page on SW3 to see if it shows the connected port roles.
Frequently asked questions
What is O-Chain and how is it different from O-Ring?
O-Ring forms a closed ring of ORing managed switches for sub-20 ms fault recovery. O-Chain extends this to an open-chain topology with a backup link — used when a closed ring is not physically possible, such as when connecting across multiple buildings or integrating with a third-party core switch. Both achieve sub-20 ms recovery. O-Ring and O-Chain cannot be active on the same switch simultaneously.
What is an Edge Port and which ports need it enabled?
Edge Port marks a port as the open end of the O-Chain. Only the two outermost ports of the entire chain should have Edge Port = Enable. In this example: SW1 Port 9 and SW2 Port 19. All other O-Chain ports connecting intermediate switches must have Edge Port = Disable. Incorrectly enabling Edge Port on an intermediate port prevents O-Chain from forming correctly.
Why must O-Ring be disabled before enabling O-Chain?
O-Ring and O-Chain are two redundancy protocols that cannot run simultaneously. Enabling both causes a protocol conflict. Always disable O-Ring first, save the configuration, then enable O-Chain. This applies to all switches in the topology.
Why must SW1 Port 9 be disconnected before configuring O-Chain?
SW1 Port 9 is the backup link that closes the chain into a physical loop when connected. During the transition from O-Ring to O-Chain, there is a brief window when no redundancy protocol is active. A connected Port 9 during this window creates an uncontrolled loop that causes broadcast storms. Disconnect Port 9 first, complete configuration on all three switches, then reconnect.
O-Chain backup link is not activating after a failure — what should I check?
Start with Edge Port settings — incorrect Edge Port configuration is the most common root cause. Verify Edge Port = Enable only on SW1 Port 9 and SW2 Port 19, confirm O-Ring is disabled on all switches, and check that configurations are saved. See the Troubleshooting section above for the full checklist.
