1. What is the Goal?

Firstly, we have to ensure that when the active SCUN fails, the standby SCUN takes over AND continues to forward traffic using the single existing upstream optical cable, even though that cable is physically plugged into only one board.

2. How to Realize the Inter-Board Protection?

Inter-board protection is implemented through the switching plane (backplane)

This means that user traffic from the standby SCUN can still reach the uplink port on the active SCUN through backplane switching. So even with only one physical uplink, protection still works.

You only need to enable inter-board protection for the uplink service profile.

3. Configuration Steps

Step 1 — Enter the uplink board interface

Example: GE0/23/0 is the uplink on the SCUN board.

enable
config
interface gigabitethernet 0/23

(This port resides on the active SCUN.)

Step 2 — Enable inter-board protection

Huawei commands:

prot-type inter-board

This tells the OLT:

• If the active SCUN fails,
• the standby SCUN will take over
• and continue using the uplink on the active SCUN through the backplane.

Step 3 — Configure the protection group for the service

(This ensures service continuity for PPPoE/Layer 3/Layer 2 services.)

Example for VLAN-based uplink:

service-port 100 vlan 100 gpon 0/1/0 ont 1 gemport 1 multi-service user-vlan 100 tag-transform translate outbound board-prot

Or for IP service:

port-protect upstream

Step 4 — Verify Protection Status

display board 0
display current-configuration interface gigabitethernet 0/23
display port-protect

You should see:

• SCUN A — Active
• SCUN B — Standby
• Protection mode: Inter-board
• Switching plane: Normal
• Protection: Enabled

4. How Protection Actually Works with One Optical Cable

So even though only one uplink is physically available, the system still achieves 1+1 control board HA + uplink protection.

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5. Notes & Best Practice

✔ Recommended:

• Both SCUN boards should be the same model, same firmware.
• Ensure the backplane switching fabric is healthy:

display fabric plane

✘ Not required:

• No need to connect a second upstream cable.
• No need to configure LACP, RSTP, or dual-homing.

6. How It Works

Finally, let’s have a clear look:

Normal (Active SCUN A running)

• Uplink fiber is physically inserted in SCUN A
• SCUN B receives all service traffic via backplane → SCUN A → uplink

When the Active SCUN A fails

1. SCUN B becomes active
2. The uplink port on SCUN A (where the fiber is plugged) is logically taken over by SCUN B (Backplane handles switching of the port resource)
3. Traffic continues through the same uplink fiber → No need to move the physical cable

Protection switchover time: typically < 50 ms

Hope this passage helps you gain a clearer understanding of how inter-board protection works with dual SCUN boards when only one uplink fiber is available. If any more questions, welcome to contact us via support@thunder-link.com.