FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * WHALEN CHAD MICHAEL   2. Issuer Name and Ticker or Trading Symbol F5 NETWORKS INC [FFIV] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) EVP, Worldwide Sales (Last) (First) (Middle) C/O F5 NETWORKS, INC., 401 ELLIOTT AVE. WEST 3. Date of Earliest Transaction (Month/Day/Year) 08/01/2018 (Street) SEATTLE, WA 98119 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 08/01/2018   M   296 (1) A $ 0 296 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Restricted Stock Unit (2)

$ 0

08/01/2018

M

213

(3)

(4)

Common Stock

213

$ 0

2,126

D

Restricted Stock Unit (2)

$ 0

08/01/2018

M

83

(5)

(4)

Common Stock

83

$ 0

415

D

Restricted Stock Unit (2)

$ 0

08/01/2018

A

3,517

(6)

(4)

Common Stock

3,517

$ 0

3,517

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
WHALEN CHAD MICHAEL C/O F5 NETWORKS, INC. 401 ELLIOTT AVE. WEST SEATTLE, WA 98119			EVP, Worldwide Sales

Signatures

/s/ Greg J. Davis by Power of Attorney		08/02/2018
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Shares acquired upon vesting of the February 1, 2017 and November 1,2017 awards of service-based Restricted Stock Units.
(2)	Each Restricted Stock Unit represents a contingent right to receive one share of F5 Networks, Inc. Common Stock on the vest date.
(3)	The service-based Restricted Stock Units (RSUs) outstanding under this 02/01/2017 grant vest as follows: 213 vest 08/01/2018, 212 vest 11/1/2018, 213 vest 2/1/2019, 212 vest 05/01/2019, 213 vest 08/01/2019, 213 vest 11/01/2019, 212 vest 02/01/2020, 213 vest 05/01/2020, 212 vest 08/01/2020, 213 vest 11/01/2020 and 213 vest 02/01/2021.
(4)	If the reporting person continues to provide services to the Company through the vest date, the corresponding number of shares of Common Stock of F5 Networks, Inc. will be issued to the reporting person on the vest date.
(5)	The service-based Restricted Stock Units (RSUs) outstanding under this 11/01/2017 grant vest as follows: 83 vest 08/01/2018, 83 vest 11/1/2018, 83 vest 2/1/2019, 83 vest 05/01/2019, 83 vest 08/01/2019, 83 vest 11/01/2019.
(6)	Restricted Stock Units will vest twenty five percent (25%) a year in consecutive equal annual installments over the following 4 year period with 25% vesting on August 1, 2019, August 1, 2020, August 1, 2021 and August 1, 2022.

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