Upon giving the "do do.do" command in the console, the entire process takes place properly except for this error. There seems to be no signal existing in the entire directory with the paths "/tb_ethernet/ethmac/wishbone", or "/tb_ethernet/eth_phy/mtxen_d". I think that it is due to this that there are many undefined signals in the simulation, which may be giving a faulty simulated output.
Please suggest any necessary changes to be made, or please make the necessary changes to fix this bug, if possible.