  The Doob graph $D(m,n)$ is a distance-regular graph with the same parameters
as the Hamming graph $H(2m+n,4)$. The maximum independent sets in the Doob
graphs are analogs of the distance-$2$ MDS codes in the Hamming graphs. We
prove that the logarithm of the number of the maximum independent sets in
$D(m,n)$ grows as $2^{2m+n-1}(1+o(1))$. The main tool for the upper estimation
is constructing an injective map from the class of maximum independent sets in
$D(m,n)$ to the class of distance-$2$ MDS codes in $H(2m+n,4)$.
