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EXHIBIT 10.23

                                F5 NETWORKS, INC.

                       NONQUALIFIED STOCK OPTION AGREEMENT

THIS NONQUALIFIED STOCK OPTION AGREEMENT (the "Agreement") is made and entered
into as of August 16, 2004 (the "Grant Date") between F5 Networks, Inc., a
Washington corporation (the "Company") and Karl Triebes ("Holder").

THE PARTIES AGREE AS FOLLOWS:

1.    Grant of Option; Grant Date. The Company hereby grants to Holder, the
right (the "Option") to purchase up to 300,000 shares of the Company's Common
Stock (the "Option Shares") at a price per share of $22.81 (the "Exercise
Price"), on the terms and conditions set forth in this Agreement. This Option is
not intended to qualify as an incentive stock option for purposes of Section 422
of the Code. The number and kind of Option Shares and the Exercise Price may be
adjusted in certain circumstances in accordance with the provisions of Section 9
below.

2.    Definitions. For purposes of this Agreement, the following terms shall be
defined as set forth below:

2.1   Affiliate. "Affiliate" means any parent corporation or subsidiary
corporation of the Company, whether now or hereafter existing.

2.2   Board. "Board" means the Board of Directors of the Company.

2.3   Code. "Code" means the Internal Revenue Code of 1986, as amended.

2.4   Common Stock. "Common Stock" means the common stock of the Company.

2.5   Continuous Service. "Continuous Service" means that Holder's service with
the Company or an Affiliate, whether as an employee or consultant, is not
interrupted or terminated. Holder's Continuous Service shall not be deemed to
have terminated merely because of a change in the capacity in which Holder
renders service to the Company or an Affiliate as an employee or consultant or a
change in the entity for which Holder renders such service, provided that there
is no interruption or termination of Holder's Continuous Service. For example, a
change in status from an employee of the Company to a consultant of an Affiliate
will not constitute an interruption of Continuous Service. The Board, in its
sole discretion, may determine whether Continuous Service shall be considered
interrupted in the case of any leave of absence approved by the Board, including
sick leave, military leave or any other personal leave.

2.6   Disability. "Disability" means the permanent and total disability of
Holder within the meaning of Section 22(e)(3) of the Code.

2.7   Expiration Date. "Expiration Date" means August 16, 2014.

2.8   Fair Market Value. "Fair Market Value" means, as of any date, the value of
the Common Stock. If the Common Stock is listed on any established stock
exchange or traded on the NASDAQ National Market or the NASDAQ Small Cap Market,
the Fair Market Value of a share of Common Stock shall be the closing sales
price for such stock (or the closing bid, if no sales were reported) as quoted
on such exchange or market (or the exchange or market with the greatest volume
of trading in the Common Stock) on the day of determination or, if the day of
determination is not a market trading day, then on the last market trading day
prior to the day of determination, as reported in The Wall Street Journal or
such other source as the Board deems reliable. In the absence of such markets
for the Common Stock, the Fair Market Value shall be determined in good faith by
the Board.

2.9   Securities Act. "Securities Act" means the Securities Act of 1933, as
amended.

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2.10  Vesting Commencement Date. "Vesting Commencement Date" shall mean Holder's
first day of continuous service with the Company.

3.    Vesting. Subject to the limitations contained herein, the Option will vest
and become exercisable with respect to 25% of the Option Shares on the first
anniversary of the Vesting Commencement Date and with respect to the remaining
Option Shares in equal monthly installments over the three years following the
Vesting Commencement Date; provided that vesting will cease upon the termination
of Holder's Continuous Service.

4.    Method of Payment of the Exercise Price. Payment of the Exercise Price is
due in full upon exercise of all or any part of the Option. Holder may elect to
make payment of the Exercise Price in cash or by check or one or more of the
following if the Company, in its sole discretion at the time the Option is
exercised, is then offering such alternatives:

(a)   Provided that at the time of exercise the Common Stock is publicly traded
and quoted regularly in The Wall Street Journal, then pursuant to a program
developed under Regulation T as promulgated by the Federal Reserve Board which,
prior to the issuance of Common Stock, results in either the receipt of cash (or
check) by the Company or the receipt of irrevocable instructions to pay the
aggregate exercise price to the Company from the sales proceeds (a "cashless
exercise").

(b)   Provided that at the time of exercise the Common Stock is publicly traded
and quoted regularly in The Wall Street Journal, then by delivery of
already-owned shares of Common Stock (valued at their Fair Market Value on the
date of exercise) if (i) either Holder has held the already-owned shares for the
period required to avoid a charge to the Company's reported earnings (generally
six months) or Holder did not acquire the already-owned shares, directly or
indirectly from the Company and (ii) Holder owns the already-owned shares free
and clear of any liens, claims, encumbrances or security interests. "Delivery"
for these purposes, in the sole discretion of the Company at the time the Option
is exercised, shall include delivery to the Company of Holder's attestation of
ownership of such shares of Common Stock in a form approved by the Company.
Notwithstanding the foregoing, the Option may not be exercised by tender to the
Company of Common Stock to the extent such tender would constitute a violation
of the provisions of any law, regulation or agreement restricting the redemption
of the Company's stock.

(c)   Provided there has been a change in control described in Section 9(c) and
the surviving corporation or acquiring corporation refuses to assume the Option
or to substitute a similar option for the Option, then by authorizing the
Company to withhold shares from the shares of the Common Stock otherwise
issuable to Holder as a result of the exercise of the Option. Notwithstanding
the foregoing, the Option may not be exercised by withholding shares of Common
Stock to the extent such withholding would constitute a violation of the
provisions of any law, regulation or agreement restricting the redemption of the
Company's stock.

5.    Whole Shares. The Option may only be exercised for whole shares.

6.    Securities Law Compliance. Notwithstanding anything to the contrary
contained herein, the Option may not be exercised unless the shares issuable
upon exercise of the Option are then registered under the Securities Act or, if
such shares are not then so registered, the Company has determined that such
exercise and issuance would be exempt from the registration requirements of the
Securities Act. The exercise of the Option must also comply with other
applicable laws and regulations governing the Option, and the Option may not be
exercised if the Company determines that the exercise would not be in material
compliance with such laws and regulations.

7.    Term. The term of the Option commences on the Grant Date and expires upon
the earliest of the following:

(a)   three (3) months after the termination of Holder's Continuous Service for
any reason other than death or Disability, provided that if during any part of
such three-month period the Option is not exercisable solely because of the
condition set forth in Section 6, the Option shall not expire until the earlier
of the Expiration Date or until it shall have been exercisable for an aggregate
period of three (3) months after the termination of Holder's Continuous Service;

(b)   twelve (12) months after the termination of Holder's Continuous Service
due to Disability;

(c)   eighteen (18) months after Holder's death if Holder dies either during
Holder's Continuous Service or within three (3) months after Holder's Continuous
Service terminates for reason other than Cause;

(d)   the Expiration Date; or

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(e)   the tenth (10th) anniversary of the Grant Date.

8.    Exercise.

(a)   The vested portion of the Option may be exercised during its term by
delivering a Notice of Exercise in the form attached hereto as Exhibit A,
together with the Exercise Price (payable in the manner set forth in Section 4)
to the Secretary of the Company, or to such other person as the Company may
designate, during regular business hours, together with such additional
documents as the Company may then require. The Option may also be exercised in
such other manner as the Company may designate or authorize.

(b)   By exercising the Option, Holder agrees that, as a condition to any
exercise of the Option, the Company may require Holder to enter an arrangement
providing for the payment by Holder to the Company of any tax withholding
obligation of the Company arising by reason of (1) the exercise of the Option or
(2) the disposition of shares acquired upon such exercise.

9.    Adjustments Upon Changes in Stock.

(a)   Capitalization Adjustments. If any change is made in the Common Stock
without the receipt of consideration by the Company (through merger,
consolidation, reorganization, recapitalization, reincorporation, stock
dividend, dividend in property other than cash, stock split, liquidating
dividend, combination of shares, exchange of shares, change in corporate
structure or other transaction not involving the receipt of consideration by the
Company), the number of Option Shares and the Exercise Price will be
appropriately adjusted by the Board, whose determination shall be final, binding
and conclusive. (The conversion of any convertible securities of the Company
shall not be treated as a transaction "without receipt of consideration" by the
Company.)

(b)   Change in Control--Dissolution or Liquidation. In the event of a
dissolution or liquidation of the Company, the Option shall be terminated if not
exercised (if applicable) prior to such event.

(c)   Change in Control--Asset Sale, Merger, Consolidation or Reverse Merger.
The Option will immediately vest 100% in the event of a change in control of the
Company consisting of: (1) a sale of substantially all of the assets of the
Company, (2) a merger or consolidation in which the Company is not the surviving
corporation or (3) a reverse merger in which the Company is the surviving
corporation but the shares of Common Stock outstanding immediately preceding the
merger are converted by virtue of the merger into other property, whether in the
form of securities, cash or otherwise.

10.   Transferability. The Option is not transferable, except by will or by the
laws of descent and distribution, and is exercisable during Holder's life only
by Holder. Notwithstanding the foregoing, by delivering written notice to the
Company, in a form satisfactory to the Company, Holder may designate a third
party who, in the event of Holder's death, shall thereafter be entitled to
exercise the Option.

11.   Not a Service Contract. This Agreement is not an employment or service
contract, and nothing in this Agreement shall be deemed to create in any way
whatsoever any obligation on Holder's part to continue in the employ of the
Company, or of the Company to continue Holder's employment. In addition, nothing
in this Agreement shall obligate the Company, its shareholders, Board, officers
or employees to continue any relationship that Holder might have as a director
or consultant for the Company.

12.   Withholding Obligations.

(a)   At the time the Option is exercised, in whole or in part, or at any time
thereafter as requested by the Company, Holder hereby authorizes withholding
from payroll and any other amounts payable to Holder, and otherwise agrees to
make adequate provision for (including by means of a "cashless exercise"
pursuant to a program developed under Regulation T as promulgated by the Federal
Reserve Board to the extent permitted by the Company), any sums required to
satisfy the federal, state, local and foreign tax withholding obligations of the
Company, which arise in connection with the Option.

(b)   The Option is not exercisable unless the tax withholding obligations of
the Company are satisfied. Accordingly, Holder may not be able to exercise the
Option when desired even though the Option is vested.

13.   No Rights As A Shareholder. The Option shall not entitle the Holder to any
cash dividend, voting or other right of a shareholder unless and until the date
of issuance of the shares that are the subject of the Option.

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14.   Professional Advice. The acceptance and exercise of the Option and the
sale of Option Shares has consequences under federal and state tax and
securities laws which may vary depending upon the individual circumstances of
the Holder. Accordingly, Holder acknowledges that he has been advised to consult
his personal legal and tax advisor in connection with this Agreement and his
dealings with respect to the Option and the Option Shares. Holder further
acknowledges that the Company has made no warranties or representations to
Holder with respect to the income tax consequences of the grant and exercise of
the Option or the sale of the Option Shares and Holder is in no manner relying
on the Company or its representatives for an assessment of such consequences.

15.   Assignment; Binding Effect. Subject to the limitations set forth in this
Agreement, this Agreement shall be binding upon and inure to the benefit of the
executors, administrators, heirs, legal representatives, and successors of the
parties hereto; provided, however, that Holder may not assign any of Holder's
rights under this Agreement.

16.   Damages. Holder shall be liable to the Company for all costs and damages,
including incidental and consequential damages, resulting from a disposition of
Option Shares which is not in conformity with the provisions of this Agreement.

17.   Governing Law. This Agreement shall be governed by, and construed in
accordance with, the laws of the State of Washington excluding those laws that
direct the application of the laws of another jurisdiction.

18.   Notices. All notices and other communications under this Agreement shall
be in writing. Unless and until Holder is notified in writing to the contrary,
all notices, communications, and documents directed to the Company and related
to the Agreement, if not delivered by hand, shall be mailed, addressed as
follows:

General Counsel
F5 Networks, Inc.
401 Elliott Ave West
Seattle, WA 98119

Unless and until the Company is notified in writing to the contrary, all
notices, communications, and documents intended for Holder and related to this
Agreement, if not delivered by hand, shall be mailed to Holder's last known
address as shown on the Company's books. Notices and communications shall be
mailed by first class mail, postage prepaid. All mailings and deliveries related
to this Agreement shall be deemed received when actually received, if by hand
delivery, and five (5) business days after mailing, if by mail.

19.   Amendment of this Agreement. The Board at any time, and from time to time,
may amend the terms of this Agreement; provided, however, that the rights under
this Agreement shall not be impaired by any such amendment unless (i) the
Company requests the consent of the Holder and (ii) Holder consents in writing.

IN WITNESS WHEREOF, the parties have executed this Option Agreement as of the
Effective Date.

                                    F5 NETWORKS, INC.

                                    By  /s/ JOHN MCADAM
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                                    Title Chief Executive Officer and President.

Holder hereby accepts and agrees to be bound by all of the terms and conditions
of this Agreement.

                                    /s/ KARL TRIEBES
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                                    Holder