Hardware bridge and corresponding physical interfaces get disabled on EdgeSWG when propagation failure is enabled

Products

• ProxySG Software - SGOS

Issue/Introduction

Hardware bridge and corresponding physical interfaces get disabled on EdgeSWG when propagation failure was enabled (#(config bridge bridge_name) propagate-failure enable).
This is seen on SG OS starting 7.4.24.1 and 7.4.8
The physical link statusinterfaces which are part of the hardware bridge shows down and this is generally seen after the device is rebooted. 
Post the reboot, the interfaces and hardware bridge never come up and in order to activate the bridge and interfaces, the device admin needs to login to the EdgeSWG appliance and manually disable/enable interfaces

Environment

Device is running in transparent mode (Physical inline) and using hardware bridge 'passthru-x:x. Propagation failure is enabled on the hardware bridge

Cause

The issue is caused because starting 7.3.24.1 and 7.4.10,  the media types were removed when an interface was disabled. 
In this particular case, the removal of media types from one port of the hardware bridge lead to it being left in down state which subsequently brought down the other port of the bridge due to propagation failure enabled. 
The bridge side handling of the propagation failure used media settings to bring up or down the interface, which gets affected when the types are removed from the interface. 

Resolution

- This issue has been addressed in SG OS starting 7.3.27.1 and 7.4.10

- This is documented in the release notes as 
SG-42108 Fixes an issue where physical interfaces and bridges were disabled after upgrading to 7.3.24.1. This issue occurred when propagation failure was enabled (#(config bridge bridge_name) propagate-failure enable ).