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

OMB APPROVAL OMB Number: 3235-0287 Expires: January 31, 2005 Estimated average burden hours per response... 0.5

(Print or Type Responses)

1. Name and Address of Reporting Person * Anderson Mark   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) Sr. VP, Worldwide Sales (Last) (First) (Middle) 401 ELLIOTT AVENUE WEST 3. Date of Earliest Transaction (Month/Day/Year) 08/01/2010 (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 08/01/2010   M   15,366 (1) A $ 0 17,639 D   Common Stock 08/02/2010   S(2)   15,366 D $ 88.5127 2,273 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.		SEC 1474 (9-02)

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 Units

$ 0

08/01/2010

M

5,303

11/01/2008

08/01/2018

Common Stock

5,303

$ 0

1,626

D

Restricted Stock Units

$ 0

08/01/2010

M

6,313

11/01/2009

08/03/2019

Common Stock

6,313

$ 0

17,345

D

Restricted Stock Units

$ 0

08/01/2010

M

3,750

11/01/2008

11/01/2017

Common Stock

3,750

$ 0

18,750

D

Restricket Stock Units

$ 0

08/02/2010

A

17,270

11/01/2010(3)

08/02/2020

Common Stock

17,270

$ 0

17,270

D

Restricted Stock Units

$ 0

08/02/2010

A

10,000

08/01/2013(4)

08/02/2020

Common Stock

10,000

$ 0

10,000

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Anderson Mark 401 ELLIOTT AVENUE WEST SEATTLE, WA 98119			Sr. VP, Worldwide Sales

Signatures

/s/ Jeffrey A. Christianson by Power of Attorney		08/03/2010
**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 received from vesting of the 11/01/2007, 8/1/2008 and 8/3/2009 restricted stock unit grants.
(2)	Sale pursuant to the terms of a 10b5-1 trading plan.
(3)	Fifty percent (50%) of the aggregate number of RSUs in the grant vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2013. 16.66% of the grant is subject to a quarterly performance vesting schedule for the period beginning August 2, 2010 through August 1, 2011, based on the Company achieving quarterly revenue and EBITDA targets during the period beginning with the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. The remaining portion of the grant is subject to the Company meeting specified performance criteria for each of the four quarters beginning with the third quarters in fiscal years 2011 and 2012 (16.66% for each period) to be set by the Compensation Committee of the Company's Board of Directors.
(4)	One hundred percent (100%) of the RSUs will vest on August 1, 2013.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.