Disadvantages are :

1.The crossbar switch is singled-layered switch.

2.At each point,there is a switch when closed,connects one of the inputs to one of the outputs.

Crossbar Switch: A Crossbar Switch connects n inputs to m outputs in a grid, using electronic micro-switches (transistors) at each cross point. The major limitation of this design is the number of crosspoints required. Connecting n inputs to m outputs using a crossbar switch requires n * m crosspoints. For example, to connect 1000 inputs to 1000 outputs requires a crossbar with 1,000,000 crosspoints. A crossbar with this number of crosspoints is impractical. Such a switch is also inefficient because statistics show that, in practice, fewer that 25 percent of the crosspoints are in use at any given time. The rest are idle.

Multistage Switch: The solution to the limitations of the crossbar switch is the Multistage Switch, which combines crossbar switches in several stages. In multistage switching, devices are linked to switches that, in turn are linked top other switches.

The design of a multistage switch depends on the number of stages and the number postages required (or desired) in each stage.

crossbar switch

: Blocking can occur when two switch inputs attempt to access the same intermediate switch channel.