The error listed in this case is discussed as an error dealing with:
Common causes of connectivity problems are as follows:
•Network adapters and switch ports have mismatching duplex levels or transfer speed settings.
•Network adapters or switches with transmission rates of 10/100 megabits per second (Mbps) do not switch over correctly. Some autosense settings may not correctly detect the speed of some network adapters.
•The network adapter is incompatible with the motherboard or other hardware or software components and drivers.
Here is a link to to the article discussing the error 121:
The error is not listed in any of our Protect Error Code documentation.
The issue is environmental and needs to be addressed locally.