mpa:

Networking in failsafe mode is currently broken on the Linksys WRT54GSv1. The UDP message about entering failsafe mode is missing, and the device does not answer ping or SSH connection attempts to 192.168.1.1 while in failsafe mode. This issue exists both in the LEDE master branch and in the 17.01.1 release.

It can be fixed by removing the following files:

target/linux/brcm47xx/base-files/lib/preinit/05_init_interfaces_brcm
target/linux/brcm47xx/base-files/lib/preinit/15_set_preinit_interface_brcm

and rebuilding the firmware. This fix was tested on the master branch.

Do these files still have a purpose? They seem to be obsoleted by

package/base-files/files/lib/preinit/10_indicate_preinit

and the device works fine without them.

How to reproduce:
The easiest way to trigger failsafe mode on this device is probably through a serial console.
There are unrelated issues with both the Power LED and the Reset button which I had to fix before I was able to enter failsafe mode. I'll report these separately.

Regards,
Mirko