Cisco has forgotten to install all the light emitting diodes (LEDs) in some routers.

The Register understands that the LTE-enabled C800 integrated service routers. models C896, C897, and C898, lack LEDs that indicate traffic is passing over the WAN. Cisco has 'fessed up to the mess in a field notice that says "... two LEDs and two resistors were not added to the bill of materials and therefore those LEDs and resistors are not populated on production units."

"As a result, GE8 and SFP8 WAN ports do not provide visual indication of the link status or data activity. The user is unable to look at the router in order to determine whether the port is active or not active."

Users affected by the problem told The Reg that soldering LEDs into place was one option mentioned by Cisco. A Borg representative denied that claim, saying "I can assure you that we won’t be asking anyone to solder their own LEDs."

The field notice suggests either using the command line interface or asking Cisco for a replacement. The form to do make such a request is helpfully included in the field notice we've linked to above.

Cisco's no stranger to engineering woes these days: in September it issued a warning that over-tightening a single screw in another router could lead to electrocution. ®