uOS 1.35 – Trunk Enhancements

Zyxel_Lynn

The uOS 1.35 release introduces two important improvements to WAN trunk behavior that address long-standing usability issues:

1. Disconnect Connections Before Falling Back
2. No Duplicate Interfaces in a Trunk

Disconnect Connections Before Falling Back

Previous Behavior

• When the active WAN interface (e.g., WAN1) failed, sessions automatically failed over to the backup (e.g., WAN2).
• If WAN1 later recovered, existing sessions on WAN2 continued to use WAN2 until they expired naturally.
• This could cause customers to stay on the backup ISP longer than intended — especially if WAN2 was a metered or expensive link.

New Option in 1.35

• A new setting has been added under Network > Interface > Trunk:

Disconnect Connections Before Falling Back

• When enabled, once WAN1 (the primary) recovers:
  • The firewall terminates all active sessions on WAN2.
  • Clients are forced to re-initiate sessions.
  • All new sessions then go out via the restored WAN1.
• When disabled (default):
  • Existing sessions continue on WAN2.
  • Only new sessions use WAN1.

When to Use It

• Enable if:
  • WAN2 is only a backup and should be used as little as possible.
  • Customer wants to minimize costs or enforce policy to always return to the primary ISP.
• Disable if:
  • The priority is no service interruption.
  • Customer wants maximum session continuity, even if traffic temporarily stays on WAN2.

No Duplicate Interfaces in a Trunk

Previous Behavior (Bug-Like)

• The GUI previously allowed the same WAN interface (e.g., GE1) to be added twice in the same trunk profile (once as Active, once as Passive).
• After applying, only the first configuration was kept, but the GUI did not warn the user.
• This created confusion and misconfigurations.

New Behavior in 1.35

• The system now performs validation.
• If you try to add the same interface twice in one trunk, an error message is displayed.
• Prevents accidental duplicate configuration.

Summary

Enhancement	Before	After (1.35)
Disconnect Connections Before Falling Back	Existing sessions on WAN2 stay there even after WAN1 recovers.	Option to terminate WAN2 sessions so all traffic returns to WAN1.
Duplicate Interfaces in Trunk	GUI allowed same interface twice; only first config applied.	Error message prevents duplicates — eliminates confusion.

Key Takeaway

These trunk enhancements give administrators more control over failover recovery and prevent configuration mistakes, improving both reliability and clarity in WAN management.