uOS 1.35 – Single Passive Interface Rule Allowed in Trunk

Zyxel_Lynn

In addition to failover improvements and duplicate interface checks, uOS 1.35 introduces a correction to how passive WAN interfaces are handled in trunk profiles.

Previous Behavior (Before 1.35)

• The GUI allowed administrators to configure multiple passive interfaces in a single trunk profile.
• However, in reality, the firewall only ever supported one passive interface.
• If multiple passives were configured, only the first passive in the list was honored.
• Subsequent interfaces set to “Passive” in the GUI were actually treated as Active in operation.

This mismatch between GUI and backend behavior caused confusion and misconfigurations.

New Behavior in 1.35

• The GUI now enforces the single passive interface rule.
• If you attempt to configure more than one passive interface in a trunk profile, an error message appears.
• This ensures that configurations always reflect actual supported behavior.

Migration Impact

• If a customer upgrades from pre-1.35 firmware with multiple passive interfaces configured:
  • After the upgrade, only the first passive interface will remain.
  • Extra passives (e.g., ISP1 set as passive in addition to ISP2) will be automatically removed.
• Customers may notice that some interfaces “disappeared” from their trunk after upgrade.
• Explanation: those interfaces were configured as unsupported additional passives.

Summary

Behavior	Before 1.35	After 1.35
Passive interfaces per trunk	GUI allowed more than one, but only first worked. Others silently became Active.	Only one Passive allowed. GUI prevents multiple-passive configs.
Upgrade effect	Extra passives remained in GUI but behaved incorrectly.	Extra passives automatically removed; only the first passive is kept.

Starting with uOS 1.35, each trunk profile supports exactly one passive interface. This aligns the GUI with actual system behavior and prevents misleading configurations.