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 * DiLullo John D   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 AVENUE WEST 3. Date of Earliest Transaction (Month/Day/Year) 11/01/2017 (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 11/01/2017   M   3,158 (1) A $ 0 7,944 D   Common Stock 11/01/2017   S   1,465 D $ 120.94 (2) 6,479 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 (3) (4)

$ 0

11/01/2017

A

10,365

(5)

(6)

Common Stock

10,365

$ 0

10,365

D

Restricted Stock Unit (3)

$ 0

11/01/2017

M

2,542

(7)

(6)

Common Stock

2,542

$ 0

20,335

D

Restricted Stock Unit (3)

$ 0

11/01/2017

M

616

(8)

(6)

Common Stock

616

$ 0

7,392

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
DiLullo John D C/O F5 NETWORKS, INC. 401 ELLIOTT AVENUE WEST SEATTLE, WA 98119			EVP, Worldwide Sales

Signatures

/s/ Greg Davis by Power of Attorney		11/03/2017
**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 November 2, 2015 and November 1, 2016 awards of service-based Restricted Stock Units.
(2)	This transaction was executed pursuant to a Rule 10b5-1 trading plan.
(3)	Each Restricted Stock Unit represents a contingent right to receive one share of F5 Networks, Inc. Common Stock on the vest date.
(4)	Concurrent with the award of 10,365 service-based Restricted Stock Units, the Company granted the reporting person additional Restricted Stock Units that vest based on performance targets ("Performance RSUs"). If the performance targets are achieved at 100%, the reporting person will receive 10,365 Performance RSUs over the vesting period; the actual number of Performance RSUs received may be more or less depending on whether and to the extent that performance is greater than or less than targets.The Performance RSUs vests over a four-year period in four equal annual installments. Performance RSUs are not reported in Table II; the underlying shares of Performance RSUs will be reported in Table I if and when the Compensation Committee of the Board of Directors determines that the performance targets have been achieved.
(5)	This November 1, 2017 award of service-based Restricted Stock Units vests in sixteen equal quarterly increments beginning February 1, 2018.
(6)	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.
(7)	This November 2, 2015 award of service-based Restricted Stock Units vests in sixteen equal quarterly increments beginning February 1, 2016.
(8)	This November 1, 2016 award of service-based Restricted Stock Units vests in sixteen equal quarterly increments beginning February 1, 2017.

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