F5 (FFIV) 8-K F5 Networks Announces Results for Second Quarter of Fiscal 2006

Exhibit 99.1

FOR IMMEDIATE RELEASE

CONTACT:	Investor Relations
	John Eldridge
	(206) 272-6571
	j.eldridge@f5.com
	Public Relations
	Alane Moran
	(206) 272-6850
	a.moran@f5.com

F5 Networks Announces Results for Second Quarter of Fiscal 2006

SEATTLE, WA—April 20, 2006—For the second quarter of fiscal 2006, F5 Networks announced revenue of $94.1 million, up 7 percent from $88.1 million in the prior quarter and 39 percent from $67.7 million in the second quarter of fiscal 2005. Net income was $16.1 million ($0.39 per diluted share), compared to $15.2 million ($0.37 per diluted share) in the prior quarter and $12.1 million ($0.31 per diluted share) in the second quarter a year ago.

During the fourth quarter of fiscal 2005, the company began expensing stock-based compensation. To facilitate a comparison of this quarter’s results with the results of prior quarters, the company is presenting pro forma net income for the second quarter and first half of fiscal 2006. Excluding stock compensation expense, net income for the second quarter of fiscal 2006 was $20.3 million ($0.49 per diluted share) compared to pro forma net income $19.0 million ($0.47 per diluted share) in the prior quarter.

A reconciliation of reported net income to pro forma net income is included on the attached Condensed Consolidated Statements of Operations.

F5 president and chief executive officer John McAdam said revenue during the second quarter grew sequentially in all international regions and across all product categories, including the company’s security offerings and its recently acquired WAN optimization and application acceleration products. “As expected, we saw strong growth in Japan, which achieved its highest quarterly revenue to date. In addition, both EMEA and Asia Pacific delivered solid sequential growth.

“The one area where we saw marked softness during the quarter was in our North American business, which was down sequentially due to a slowdown in our US Federal business during the last few weeks of the quarter. Excluding US Federal revenue, North American revenue was up sequentially from the prior quarter.”

F5 Networks Announces Results for Second Quarter of Fiscal 2006 page 2 of 3

During the third quarter, McAdam said he expects continued sequential growth tempered by seasonal softness that characterizes the first quarter of Japan’s fiscal year. Accordingly, management has set a revenue target of $96 million to $98 million and an earnings target of $0.40 to $0.41 per diluted share, including charges for stock-based compensation. Excluding the compensation charges, the anticipated earnings range is expected to be $0.50 to $0.51 per diluted share. A reconciliation of the company’s expected reported and pro forma earnings is provided in the following table:

	Three months ended
	June 30, 2006
Reconciliation of Expected Pro Forma Third Quarter Earnings	Low		High
Net income	$	16,800	$	17,200
Stock-based compensation expense, net of tax		4,300		4,300
Pro forma net income excluding stock-based compensation expense	$	21,100	$	21,500
Net income per share — diluted	$	0.40	$	0.41
Pro forma net income per share — diluted	$	0.50	$	0.51

About F5 Networks

F5 Networks is the global leader in Application Delivery Networking. F5 provides solutions that make applications secure, fast, and available for everyone, helping organizations get the most out of their investment. By adding intelligence and manageability into the network to offload applications, F5 optimizes applications and allows them to work faster and consume fewer resources. F5’s extensible architecture intelligently integrates application optimization, protects the application and the network, and delivers application reliability — all on one universal platform. The company is headquartered in Seattle, Washington with offices worldwide. For more information, go towww.f5.com.

Forward Looking Statements

Statements in this press release concerning revenue and earnings target ranges, with and without the charge for stock-based compensation, and other statements that are not historical facts are forward-looking statements. Such forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or industry results, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors include, among others: customer acceptance of our new traffic management, security, application delivery and WAN optimization offerings; the timely development, introduction and acceptance of additional new products and features by us or our competitors; competitive pricing pressures; increased sales discounts; our ability to sustain, develop and effectively utilize distribution relationships; our ability to attract, train and retain qualified product development, marketing, sales, professional services and customer support personnel; our ability to expand in international markets and the unpredictability of our sales cycle.

F5 Networks Announces Results for Second Quarter of Fiscal 2006 page 3 of 3

We have no duty to update any guidance provided or other matters discussed in this press release. More information about potential risk factors that could affect our business and financial results is included in our annual report on Form 10-K for the fiscal year ended September 30, 2005, and other public filings with the Securities and Exchange Commission.

# # # #

F5 Networks, Inc.
Consolidated Balance Sheets
(unaudited, in thousands)

	March 31,			September 30,
	2006			2005
Assets
Current assets
Cash and cash equivalents	$	23,003		$	51,867
Short-term investments		321,003			184,314
Accounts receivable, net of allowances of $2,309 and $2,969		51,953			41,703
Inventories		3,024			2,699
Deferred tax assets		3,942			3,935
Other current assets		12,266			9,906
Total current assets		415,191			294,424
Restricted cash		3,870			3,871
Property and equipment, net		23,669			16,158
Long-term investments		76,009			128,834
Deferred tax assets		19,682			36,212
Goodwill		81,652			49,677
Other assets, net		16,674			8,323
Total assets	$	636,747		$	537,499
Liabilities and Shareholders’ Equity
Current liabilities
Accounts payable	$	14,605		$	7,668
Accrued liabilities		23,042			19,648
Deferred revenue		44,256			36,009
Total current liabilities		81,903			63,325
Other long-term liabilities		7,580			6,650
Deferred revenue, long-term		3,650			3,314
Total long-term liabilities		11,230			9,964
Commitments and contingencies
Shareholders’ equity
Preferred stock, no par value; 10,000 shares authorized, no shares outstanding		—			—
Common stock, no par value; 100,000 shares authorized, 40,388 and 38,593 shares issued and outstanding		460,789			412,419
Accumulated other comprehensive loss		(1,684	)		(1,430	)
Retained earnings		84,509			53,221
Total shareholders’ equity		543,614			464,210
Total liabilities and shareholders’ equity	$	636,747		$	537,499

F5 Networks, Inc.
Condensed Consolidated Statements of Operations
(unaudited, in thousands, except per share amounts)

	Three months ended					Six months ended
	March 31,					March 31,
	2006			2005		2006			2005
Net revenues
Products	$	72,775		$	53,332	$	141,366		$	99,729
Services		21,341			14,398		40,837			28,010
Total		94,116			67,730		182,203			127,739
Cost of net revenues (1)
Products		15,441			11,820		30,034			22,348
Services		5,846			3,908		10,820			7,294
Total		21,287			15,728		40,854			29,642
Gross Profit		72,829			52,002		141,349			98,097
Operating expenses (1)
Sales and marketing		31,162			20,885		60,027			40,525
Research and development		12,276			7,789		22,754			14,763
General and administrative		7,148			5,854		14,545			10,860
Total		50,586			34,528		97,326			66,148
Income from operations		22,243			17,474		44,023			31,949
Other income, net		3,877			1,641		6,847			3,028
Income before income taxes		26,120			19,115		50,870			34,977
Provision for income taxes (1)		10,053			7,003		19,582			12,872
Net Income	$	16,067		$	12,112	$	31,288		$	22,105
Net income per share — basic	$	0.40		$	0.33	$	0.79		$	0.61
Weighted average shares — basic		40,120			36,905		39,636			36,234
Net income per share — diluted	$	0.39		$	0.31	$	0.76		$	0.58
Weighted average shares — diluted		41,627			38,921		41,278			38,394
Reconciliation to pro forma results
Net income as reported	$	16,067				$	31,288
Stock-based compensation expense, net of tax		4,235					8,054
Pro forma net income	$	20,302				$	39,342
Pro forma net income per share — diluted	$	0.49				$	0.95
Pro forma weighted average shares — diluted		41,627					41,278
(1) Includes stock-based compensation as follows:
Cost of net revenues	$	349				$	698
Sales and marketing		2,200					4,289
Research and development		1,535					2,978
General and administrative		1,508					2,878
Tax effect of stock based compensation		(1,357	)				(2,789	)
		4,235					8,054