  We investigate noise effects on the performance of entanglement distribution
by separable state. We consider a realistic situation in which the mediating
particle between two distant nodes of the network goes through a noisy channel.
For a large class of noise models we show that the average value of distributed
entanglement between two parties is equal to entanglement between particular
bipartite partitions of target qubits and exchange qubit in intermediate steps
of the protocol. This result is valid for distributing two qubit/qudit and
three qubit entangled states. In explicit examples of the noise family, we show
that there exists a critical value of noise parameter beyond which distribution
of distillable entanglement is not possible. Furthermore, we determine how this
critical value increases in terms of Hilbert space dimension, when distributing
$d$-dimensional Bell states.
