Exhibit 31.1

                                 CERTIFICATIONS

I, John McAdam, certify that:

     1)   I have reviewed this quarterly report on Form 10-Q of F5 Networks,
          Inc.

     2)   Based on my knowledge, this quarterly report does not contain any
          untrue statement of a material fact or omit to state a material fact
          necessary to make the statements made, in light of the circumstances
          under which such statements were made, not misleading with respect to
          the period covered by this quarterly report;

     3)   Based on my knowledge, the financial statements, and other financial
          information included in this quarterly report, fairly present in all
          material respects the financial condition, results of operations and
          cash flows of the registrant as of, and for, the periods presented in
          this quarterly report;

     4)   The registrant's other certifying officer and I are responsible for
          establishing and maintaining disclosure controls and procedures (as
          defined in Exchange Act Rules 13a-14 and 15d-14) for the registrant
          and have:

          a)   designed such disclosure controls and procedures, or caused such
               disclosure controls and procedures to be designed under our
               supervision, to ensure that material information relating to the
               registrant, including its consolidated subsidiaries, is made
               known to us by others within those entities, particularly during
               the period in which this quarterly report is being prepared;

          b)   evaluated the effectiveness of the registrant's disclosure
               controls and procedures and presented in this quarterly report
               our conclusions about the effectiveness of the disclosure
               controls and procedures, as of the end of the period covered by
               this report based on such evaluation; and

          c)   disclosed in this report any change in the registrant's internal
               controls over financial reporting that occurred during our most
               recent fiscal quarter that has materially affected, or is
               reasonably likely to materially affect, the registrant's internal
               controls over financial reporting; and

     5)   The registrant's other certifying officer and I have disclosed, based
          on our most recent evaluation, to the registrant's auditors and the
          audit committee of registrant's board of directors (or persons
          performing the equivalent functions):

          a)   all significant deficiencies in the design or operation of
               internal controls over financial reporting which are reasonably
               likely to adversely affect the registrant's ability to record,
               process, summarize and report financial data; and any fraud,
               whether or not material, that involves management or other
               employee who have a significant role in the registrant's internal
               controls over financial reporting.


Date: August 12, 2003



/s/ JOHN MCADAM
- --------------------
John McAdam
Chief Executive Officer and President

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