Bug ID 693910: Traffic Interruption for MAC Addresses Learned on Interfaces that Enter Blocked STP State (2000/4000/i2800/i4800 series)

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
11.6.0, 11.6.1, 11.6.2, 11.6.3,,,,, 11.6.4, 11.6.5,,,, 12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2, 12.1.0, 12.1.1, 12.1.2, 12.1.3,,,,,,,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0,,,,,

Fixed In:
14.0.0,, 12.1.4

Opened: Nov 10, 2017

Severity: 3-Major


Some MAC addresses might experience delayed forwarding after the interface on which they are learned transition to a STP blocked state. This is because the FDB entries are not being flushed on these interfaces after they change to a block state. Traffic destined to these MAC addresses gets dropped until their associated entries in the FDB age out.


Traffic interruption for up to a few minutes for MAC addresses learned on the affected interface.


MAC addresses are learned on a STP forwarding interface that transitions to a blocked interface following a topology change.



Fix Information

FDB entries are now flushed by interface whenever an interface transitions to a STP block state.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips