Numpy: Get random set of rows from 2D array

I have a very large 2D array which looks something like this:

a=
[[a1, b1, c1],
 [a2, b2, c2],
 ...,
 [an, bn, cn]]

Using numpy, is there an easy way to get a new 2D array with, e.g., 2 random rows from the initial array a (without replacement)?

e.g.

b=
[[a4,  b4,  c4],
 [a99, b99, c99]]