documentclass{article}

begin{table}
centering
begin{tabular}{|l|c|c|c|}
    hlinebackslashbox{Enhed}{Interface} & ED    & DDG   & textit{Server} \
    hline  ED      & checkmark        & checkmark        & {cellcolor{Gray}} \
    hline DDG     & checkmark        & {cellcolor{Gray}}  & checkmark \
    hline textit{Server}  & {cellcolor{Gray}}  & checkmark        & {cellcolor{Gray}}\hline
end{tabular}
caption{Oversigt over interfaces mellem enhederne.}
label{tab:interfacesMellemEnheder}
end{table}
end{document}