\def\n{5}
\def\radius{2cm}

\foreach \i in {1,...,\n} 
    \node[draw, small vertex] (v\i) at ({-360/\n * (\i)}:\radius) {};
    
\foreach \u in {1,...,\n}
    \foreach \v in {\u,...,\n}
        \draw (v\u) -- (v\v);