X0306 4 2013-12-09 0 0001484504 Gigamon Inc. GIMO 0001267021 DESIMONE DAVID ANTHONY C/O GIGAMON INC. 598 GIBRALTAR DRIVE MILPITAS CA 95035 0 1 0 0 VP Engineering & Wwide Support Common Stock 2013-12-09 4 F 0 4639 29.27 D 64693 D The shares reported as disposed of were withheld by the Issuer in order to cover withholding taxes in connection with the vesting of restricted stock units, or RSUs. These shares were not issued to or sold by the reporting person. All shares are represented by RSUs. All share numbers and per share prices disclosed in this Form 4 give effect to the Issuer's one-for-three reverse stock split completed on May 20, 2013. /s/ Paul Shinn, Attorney-in-Fact 2013-12-10