JUNIPER NETWORKS, INC. 3.100% Senior Notes due 2016 4.600% Senior Notes due 2021 5.950% Senior Notes due 2041 UNDERWRITING AGREEMENT

Exhibit 1.1

JUNIPER NETWORKS, INC.

3.100% Senior Notes due 2016

4.600% Senior Notes due 2021

5.950% Senior Notes due 2041

UNDERWRITING AGREEMENT

February 28, 2011

To the Managers named in Schedule I hereto

for the Underwriters named in Schedule II hereto

Ladies and Gentlemen:

Juniper Networks, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to the several underwriters named in Schedule II hereto (the “Underwriters”), for whom you are acting as managers (the “Managers”), the principal amount of its debt securities identified in Schedule I hereto (the “Securities”), to be issued under the indenture dated as of the Closing Date (as defined herein) (the “Base Indenture”) between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”) together with a supplemental indenture to be entered into between the Company and the Trustee as of the Closing Date with respect to the Securities (the “Supplemental Indenture” and, together with the Base Indenture, the “Indenture”). If the firm or firms listed in Schedule II hereto include only the Managers listed in Schedule I hereto, then the terms “Underwriters” and “Managers” as used herein shall each be deemed to refer to such firm or firms.

The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement, including a prospectus, (the file number of which is set forth in Schedule I hereto) on Form S-3, relating to securities (the “Shelf Securities”), including the Securities, to be issued from time to time by the Company. The registration statement as amended to the date of this Agreement, including the information (if any) deemed to be part of the registration statement at the time of effectiveness pursuant to Rule 430A or Rule 430B under the Securities Act of 1933, as amended (the “Securities Act”), is hereinafter referred to as the “Registration Statement,” and the related prospectus covering the Shelf Securities dated September 3, 2010 in the form first used to confirm sales of the Securities (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Basic Prospectus.” The Basic Prospectus, as supplemented by the prospectus supplement specifically relating to the Securities in the form first used to confirm sales of the Securities (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Prospectus,” and the term “preliminary prospectus” means any preliminary form of the Prospectus. For purposes of this Agreement, “free writing prospectus” has the meaning set forth in Rule 405 under the Securities Act, “Time of Sale Prospectus” means the preliminary prospectus together with the free writing prospectuses, if any, each identified in Schedule I hereto, and “broadly available road show” means a “bona fide electronic road show” as defined in Rule 433(h)(5) under the Securities Act that has been made available without restriction to any person. As used herein, the terms “Registration Statement,” “Basic Prospectus,” “preliminary prospectus,”

“Time of Sale Prospectus” and “Prospectus” shall include the documents, if any, incorporated by reference therein. The terms “supplement,” “amendment,” and “amend” as used herein with respect to the Registration Statement, the Basic Prospectus, the Time of Sale Prospectus, any preliminary prospectus or free writing prospectus shall include all documents subsequently filed by the Company with the Commission pursuant to the Securities Exchange Act of 1934, as amended (the “Exchange Act”), that are deemed to be incorporated by reference therein.

1. Representations and Warranties. The Company represents and warrants to and agrees with each of the Underwriters that:

(a) The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or threatened by the Commission.

(b) (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) each part of the Registration Statement, when such part became effective, did not contain, and each such part, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement as of the date hereof does not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iv) the Registration Statement and the Prospectus comply, and as amended or supplemented, if applicable, will comply in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder, (v) the Time of Sale Prospectus does not, and at the time of each sale of the Securities in connection with the offering when the Prospectus is not yet available to prospective purchasers and at the Closing Date (as defined in Section 4), the Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (vi) each broadly available road show, if any, when considered together with the Time of Sale Prospectus, does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading and (vii) the Prospectus does not contain and, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material

fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to (A) statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus based upon information relating to any Underwriter furnished to the Company in writing by such Underwriter through the Managers expressly for use therein or (B) that part of the Registration Statement that constitutes the Statement of Eligibility (Form T-1) under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”), of the Trustee.

(c) The Company is not an “ineligible issuer” in connection with the offering pursuant to Rules 164, 405 and 433 under the Securities Act. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or behalf of or used or referred to by the Company complies or will comply in all material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule I hereto, and electronic road shows, if any, each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

(d) The Company has been duly incorporated, is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation, has the corporate power and authority to own its property and to conduct its business as described in the Time of Sale Prospectus and is duly qualified to transact business and is in good standing in each jurisdiction in which the conduct of its business or its ownership or leasing of property requires such qualification, except to the extent that the failure to be so qualified or be in good standing would not have a Material Adverse Effect (as defined in Section 1(k) below).

(e) Each “significant subsidiary” (as defined in Rule 1-02 of Regulation S-X under the Exchange Act) of the Company (each, a “Significant Subsidiary”) has been duly incorporated, is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation, has the corporate power and authority to own its property and to conduct its business as described in the Time of Sale Prospectus and is duly qualified to transact business and is in good standing in each jurisdiction in which the conduct of its business or its ownership or leasing of property requires such qualification, except to the extent that the failure

to be so qualified or be in good standing would not have a Material Adverse Effect; all of the issued shares of capital stock or membership interests of each Significant Subsidiary of the Company have been duly and validly authorized and issued, are fully paid and non-assessable and are owned directly or indirectly by the Company (except for director qualifying shares or similar requirements), free and clear of all liens, encumbrances, equities or claims. The subsidiaries listed on Exhibit 21.1 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2010 are the only “Significant Subsidiaries” of the Company.

(f) This Agreement has been duly authorized, executed and delivered by the Company.

(g) On the Closing Date, the Indenture will have been duly qualified under the Trust Indenture Act and will be duly authorized, executed and delivered by, and will be a valid and binding agreement of, the Company, enforceable in accordance with its terms, subject, as to enforcement, to bankruptcy, insolvency, reorganization and other laws of general applicability relating to or affecting creditors’ rights and to general equity principles, including principles of commercial reasonableness, good faith and fair dealing (the “Enforceability Exceptions”).

(h) The Securities have been duly authorized and, when executed and authenticated in accordance with the provisions of the Indenture and delivered to and paid for by the Underwriters in accordance with the terms of this Agreement, will be valid and binding obligations of the Company, enforceable in accordance with their terms, subject to the Enforceability Exceptions, and will be entitled to the benefits of the Indenture.

(i) The execution and delivery by the Company of, and the performance by the Company of its obligations under, this Agreement, the Indenture and the Securities, will not contravene any provision of (i) applicable law or (ii) the certificate of incorporation or by-laws of the Company or (iii) any agreement or other instrument binding upon the Company or any of its Significant Subsidiaries, or (iv) any judgment, order or decree of any governmental body, agency or court having jurisdiction over the Company or any Significant Subsidiary, except, in the case of clauses (i), (iii) or (iv), as would not, individually or on the aggregate, have a Material Adverse Effect; and no consent, approval, authorization or order of, or qualification with, any governmental body or agency is required for the performance by the Company of its obligations under this Agreement, the Indenture or the Securities, except such as may be required by the securities or Blue Sky laws of the various states in connection with the offer and sale of the Securities or as contemplated by this Agreement, the Indenture and the Securities.

(j) There has not occurred any material adverse change, or any development involving a prospective material adverse change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company and its Significant Subsidiaries, taken as a whole, from that set forth in the Time of Sale Prospectus.

(k) There are no legal or governmental proceedings pending or threatened to which the Company or any of its Significant Subsidiaries is a party or to which any of the properties of the Company or any of its Significant Subsidiaries is subject (i) other than proceedings accurately described in all material respects in the Time of Sale Prospectus and proceedings that would not have a material adverse effect on the Company and its Significant Subsidiaries, taken as a whole, or on the power or ability of the Company to perform its obligations under this Agreement, the Indenture or the Securities or to consummate the transactions contemplated by the Time of Sale Prospectus (a “Material Adverse Effect”) or (ii) that are required to be described in the Registration Statement or the Prospectus and are not so described; and there are no statutes, regulations, contracts or other documents that are required to be described in the Registration Statement or the Prospectus or to be filed as exhibits to the Registration Statement that are not described or filed as required.

(l) Each preliminary prospectus filed as part of the registration statement as originally filed or as part of any amendment thereto, or filed pursuant to Rule 424 under the Securities Act, complied when so filed in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder.

(m) The Company is not, and after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Prospectus will not be, required to register as an “investment company” as such term is defined in the Investment Company Act of 1940, as amended.

(n) The Company and its Significant Subsidiaries (i) are in compliance with any and all applicable foreign, federal, state and local laws and regulations relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants (“Environmental Laws”), (ii) have received all permits, licenses or other approvals required of them under applicable Environmental Laws to conduct their respective businesses as currently conducted and (iii) are in compliance with all terms and conditions of any such permit, license or approval, except where such noncompliance with Environmental Laws, failure to receive required permits, licenses or other approvals or failure to comply with the terms and conditions of such

permits, licenses or approvals would not, singly or in the aggregate, have a Material Adverse Effect.

(o) Neither the Company nor any of its subsidiaries or affiliates, nor any director, officer, or employee, nor, to the Company’s knowledge, any agent or representative of the Company or of any of its subsidiaries or affiliates, has taken or will take any action in furtherance of an offer, payment, promise to pay, or authorization or approval of the payment or giving of money, property, gifts or anything else of value, directly or indirectly, to any “government official” (including any officer or employee of a government or government-owned or controlled entity or of a public international organization, or any person acting in an official capacity for or on behalf of any of the foregoing, or any political party or party official or candidate for political office) to influence official action or secure an improper advantage in violation of applicable law; and the Company and its subsidiaries and affiliates have conducted their businesses in compliance with applicable anti-corruption laws and have instituted and maintain and will continue to maintain policies and procedures designed to promote and achieve compliance with such laws and with the representation and warranty contained herein.

(p) (i) Except as disclosed in the Time of Sale Prospectus and the Prospectus, (x) the Company and its Significant Subsidiaries own or possess, or can acquire or license on reasonable terms, all material patents, patent applications, inventions, trademarks, service marks, trade names, trademark registrations, service xxxx registrations, domain names, copyrights, copyright applications, licenses, know-how (including trade secrets and other unpatented and/or unpatentable proprietary or confidential information, systems or procedures) and other intellectual property (“Intellectual Property”) currently employed by them in the conduct of their respective businesses, except for such failures to own or possess, or to acquire or license on reasonable terms, as would not have a Material Adverse Effect, and (y) to the Company’s knowledge, all Intellectual Property owned by the Company and its Significant Subsidiaries is free and clear of all liens, encumbrances, defects or other restrictions (including, without limitation, those imposed by any judgment, order, writ, injunction or decree of any arbitrator, court or other governmental authority), except as would not materially impair the conduct of the business of the Company and its Significant Subsidiaries as currently conducted, taken as a whole. (ii) Except as disclosed in the Time of Sale Prospectus and the Prospectus, to the Company’s knowledge, (x) there is no pending lawsuit or legal proceeding brought by a third party that claims that the Company or any of its Significant Subsidiaries infringes or misappropriates any Intellectual Property owned by such third party that, if the subject of an unfavorable decision, would be reasonably expected to have a material adverse effect on the Company and its Significant Subsidiaries, taken as a whole, and (y) none of the Intellectual

Property owned by the Company and its Significant Subsidiaries is invalid or unenforceable, except for Intellectual Property the invalidity or unenforceability of which would not have a material adverse effect on the Company and its Significant Subsidiaries, taken as a whole.

(q) (i) To the Company’s knowledge, except as disclosed in the Time of Sale Prospectus and the Prospectus, the operations of the Company and its subsidiaries are and have been conducted at all times in material compliance with all applicable financial recordkeeping and reporting requirements, including, as applicable, those of the Bank Secrecy Act, as amended by Title III of the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 (USA PATRIOT Act), and the applicable anti-money laundering statutes of jurisdictions where the Company and its subsidiaries conduct business, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Anti-Money Laundering Laws”); and (ii) no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Anti-Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(r) Except, in the case of (i) and (iii) below, with all necessary licenses and approvals required by applicable law:

(i) The Company represents that neither the Company nor any of its subsidiaries, nor any director, officer, or employee thereof nor, to the Company’s knowledge, any agent, affiliate or representative of the Company or any of its subsidiaries, is an individual or entity (“Person”) that is, or is owned or controlled by a Person that is:

(A) the subject of any sanctions administered or enforced by the U.S. Department of Treasury’s Office of Foreign Assets Control (“OFAC”), the United Nations Security Council (“UNSC”), the European Union (“EU”), Her Majesty’s Treasury (“HMT”), or other relevant sanctions authority (collectively, “Sanctions”), nor

(B) located, organized or resident in a country or territory that is the subject of Sanctions (including, without limitation, Burma/Myanmar, Cuba, Iran, North Korea, Sudan and Syria);

(ii) The Company represents and covenants that it will not, directly or indirectly, use the proceeds of the offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other Person:

(A) to fund or facilitate any activities or business of or with any Person or in any country or territory that, at the time of such funding or facilitation, is the subject of Sanctions; or

(B) in any other manner that will result in a violation of Sanctions by any Person (including any Person participating in the offering, whether as underwriter, advisor, investor or otherwise).

(iii) The Company represents and covenants that it and its subsidiaries have not knowingly engaged in, are not now knowingly engaged in, and will not engage in, any dealings or transactions with any Person, or in any country or territory, that at the time of the dealing or transaction is or was the subject of Sanctions.

(s) Except as disclosed in the Time of Sale Prospectus and the Prospectus, (i) the Company and each of its Significant Subsidiaries have filed all federal, state, local and foreign tax returns required to be filed through the date of this Agreement or have requested extensions thereof (except where the failure to file would not, individually or in the aggregate, have a material adverse effect) and have paid all taxes required to be paid thereon (except for cases in which the failure to file or pay would not have a material adverse effect, or, except as currently being contested in good faith and for which reserves required by U.S. GAAP, if any, have been created in the financial statements of the Company), and (ii) no tax deficiency has been determined adversely to the Company or any of its Significant Subsidiaries which has had (nor does the Company nor any of its Significant Subsidiaries have any notice or knowledge of any tax deficiency which could reasonably be expected to have) a Material Adverse Effect.

(t) The Company maintains a system of internal control over financial reporting (as such term is defined in Rule 13a-15(f) of the Exchange Act) that complies with the requirements of the Exchange Act. The Company’s internal control over financial reporting is effective based on the criteria established in “Internal Control — Integrated Framework” issued by the Committee of Sponsoring Organizations of the Xxxxxxxx Commission; and the Company is not aware of any material weaknesses in its internal control over financial reporting.

(u) Since the date of the latest audited financial statements included or incorporated by reference in the Time of Sale Prospectus, there has been no change in the Company’s internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting.

(v) The Company maintains disclosure controls and procedures (as such term is defined in Rule 13a-15(e) of the Exchange Act) that

comply with the requirements of the Exchange Act; such disclosure controls and procedures have been designed to ensure that material information relating to the Company and its consolidated subsidiaries is made known to the Company’s principal executive officer and principal financial officer by others within those entities; and such disclosure controls and procedures are effective such that the information relating to the Company required to be disclosed in its reports required to be filed with the Commission pursuant to Section 13 or 15(d) of the Exchange Act (i) is recorded, processed, summarized, and reported within the time periods specified in Commission rules and forms, and (ii) is accumulated and communicated to the Company’s management as appropriate to allow timely decisions regarding required disclosure.

(w) There is and has been no material failure on the part of the Company or, to the Company’s knowledge, any of the Company’s directors or officers, in their capacities as such, to comply with any provision of the Xxxxxxxx-Xxxxx Act of 2002 and the rules and regulations promulgated in connection therewith, including Section 402 related to loans and Sections 302 and 906 related to certifications.

2. Agreements to Sell and Purchase. The Company hereby agrees to sell to the several Underwriters, and each Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to purchase from the Company the respective principal amounts of Securities set forth in Schedule II hereto opposite its name at the purchase price set forth in Schedule I hereto.

3. Public Offering. The Company is advised by you that the Underwriters propose to make a public offering of their respective portions of the Securities as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable. The Company is further advised by you that the Securities are to be offered to the public upon the terms set forth in the Prospectus.

4. Payment and Delivery. Payment for the Securities shall be made to the Company in Federal or other funds immediately available in New York City on the closing date and time set forth in Schedule I hereto, or at such other time on the same or such other date, not later than the fifth business day thereafter, as may be designated in writing by you. The time and date of such payment are hereinafter referred to as the “Closing Date.”

Payment for the Securities shall be made against delivery to you on the Closing Date for the respective accounts of the several Underwriters of the Securities registered in such names and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date, with transfer taxes, if any, payable in connection with the transfer of the Securities to the Underwriters duly paid.

5. Conditions to the Underwriters’ Obligations. The several obligations of the Underwriters are subject to the following conditions:

(a) Subsequent to the execution and delivery of this Agreement and prior to the Closing Date:

(i) there shall not have occurred any downgrading, nor shall any notice have been given of any intended or potential downgrading or of any review for a possible change that does not indicate the direction of the possible change, in the rating accorded the Company or any of the securities of the Company or any of its Significant Subsidiaries by any “nationally recognized statistical rating organization,” as such term is defined for purposes of Rule 436(g)(2) under the Securities Act; and

(ii) there shall not have occurred any change, or any development involving a prospective change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company and its Significant Subsidiaries, taken as a whole, from that set forth in the Time of Sale Prospectus as of the date of this Agreement that, in your judgment, is material and adverse and that makes it, in your judgment, impracticable to market the Securities on the terms and in the manner contemplated in the Time of Sale Prospectus.

(b) The Underwriters shall have received on the Closing Date a certificate, dated the Closing Date and signed by an executive officer of the Company, to the effect set forth in Section 5(a)(i) above and to the effect that the representations and warranties of the Company contained in this Agreement are true and correct as of the Closing Date and that the Company has complied in all material respects with all of the agreements and satisfied all of the conditions on its part to be performed or satisfied hereunder on or before the Closing Date. The officer signing and delivering such certificate may rely upon his or her knowledge as to proceedings threatened.

(c) The Underwriters shall have received on the Closing Date an opinion of Xxxxxx Xxxxxxx Xxxxxxxx & Xxxxxx Professional Corporation, outside counsel for the Company, dated the Closing Date, substantially in the form attached hereto as Annex A.

(d) The Underwriters shall have received on the Closing Date an opinion of Xxxxx Xxxx & Xxxxxxxx LLP, counsel for the Underwriters, dated the Closing Date, in form and substance satisfactory to the Managers.

The opinion of counsel for the Company described in Section 5(c) above shall be rendered to the Underwriters at the request of the Company and shall so state therein.

(e) The Underwriters shall have received, on each of the date hereof and the Closing Date, a letter dated the date hereof or the Closing Date, as the case may be, in form and substance satisfactory to the Underwriters, from Ernst & Young LLP, independent public accountants, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information contained in the Registration Statement, the Time of Sale Prospectus and the Prospectus; provided that the letter delivered on the Closing Date shall use a “cut-off date” not earlier than the date hereof.

6. Covenants of the Company. The Company covenants with each Underwriter as follows:

(a) To furnish to you, without charge, a signed copy of the Registration Statement (including exhibits thereto and documents incorporated by reference therein) and to deliver to each of the Underwriters during the period mentioned in Section 6(e) or 6(f) below, as many copies of the Time of Sale Prospectus, the Prospectus, any documents incorporated by reference therein and any supplements and amendments thereto or to the Registration Statement as you may reasonably request.

(b) Before amending or supplementing the Registration Statement, the Time of Sale Prospectus or the Prospectus, to furnish to you a copy of each such proposed amendment or supplement and not to file any such proposed amendment or supplement to which you reasonably object.

(c) To furnish to you a copy of each proposed free writing prospectus to be prepared by or on behalf of, used by, or referred to by the Company and not to use or refer to any proposed free writing prospectus to which you reasonably object.

(d) Not to take any action that would result in an Underwriter or the Company being required to file with the Commission pursuant to Rule 433(d) under the Securities Act a free writing prospectus prepared by or on behalf of the Underwriter that the Underwriter otherwise would not have been required to file thereunder.

(e) If the Time of Sale Prospectus is being used to solicit offers to buy the Securities at a time when the Prospectus is not yet available to prospective purchasers and any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Time of Sale Prospectus in order to make the statements therein, in the light of the circumstances, not misleading, or if any event shall occur or condition exist as a result of which the Time of Sale Prospectus conflicts with the

information contained in the Registration Statement then on file, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Time of Sale Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to any dealer upon request, either amendments or supplements to the Time of Sale Prospectus so that the statements in the Time of Sale Prospectus as so amended or supplemented will not, in the light of the circumstances when the Time of Sale Prospectus is delivered to a prospective purchaser, be misleading or so that the Time of Sale Prospectus, as amended or supplemented, will no longer conflict with the Registration Statement, or so that the Time of Sale Prospectus, as amended or supplemented, will comply with applicable law.

(f) If, during such period after the first date of the public offering of the Securities as in the opinion of counsel for the Underwriters the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is required by law to be delivered in connection with sales by an Underwriter or dealer, any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Prospectus in order to make the statements therein, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is delivered to a purchaser, not misleading, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to the dealers (whose names and addresses you will furnish to the Company) to which Securities may have been sold by you on behalf of the Underwriters and to any other dealers upon request, either amendments or supplements to the Prospectus so that the statements in the Prospectus as so amended or supplemented will not, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is delivered to a purchaser, be misleading or so that the Prospectus, as amended or supplemented, will comply with applicable law.

(g) To endeavor to qualify the Securities for offer and sale under the securities or Blue Sky laws of such jurisdictions as you shall reasonably request; provided that in connection therewith the Company shall not be required to qualify as a foreign corporation or to file a general consent to service of process in any jurisdiction or assume any ongoing reporting obligations to any governmental or other authorities in any jurisdiction.

(h) To the extent not available on the Commission’s XXXXX filing system (or any successor system), to make generally available to the Company’s security holders and to you as soon as practicable an earning

statement covering a period of at least twelve months beginning with the first fiscal quarter of the Company occurring after the date of this Agreement which shall satisfy the provisions of Section 11(a) of the Securities Act and the rules and regulations of the Commission thereunder.

(i) Whether or not the transactions contemplated in this Agreement are consummated or this Agreement is terminated, to pay or cause to be paid all expenses incident to the performance of its obligations under this Agreement, including: (i) the fees, disbursements and expenses of the Company’s counsel and the Company’s accountants in connection with the registration and delivery of the Securities under the Securities Act and all other fees or expenses in connection with the preparation and filing of the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, any free writing prospectus prepared by or on behalf of, used by, or referred to by the Company and amendments and supplements to any of the foregoing, including the filing fees payable to the Commission relating to the Securities, all printing costs associated therewith, and the mailing and delivering of copies thereof to the Underwriters and dealers, in the quantities hereinabove specified, (ii) all costs and expenses related to the transfer and delivery of the Securities to the Underwriters, including any transfer or other taxes payable thereon, (iii) the cost of printing or producing any Blue Sky or legal investment memorandum in connection with the offer and sale of the Securities under state securities laws and all expenses in connection with the qualification of the Securities for offer and sale under state securities laws as provided in Section 6(g) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection with such qualification and in connection with the Blue Sky or legal investment memorandum, (iv) any fees charged by the rating agencies for the rating of the Securities, (v) the cost of the preparation, issuance and delivery of the Securities, (vi) the costs and charges of any trustee, transfer agent, registrar or depositary, (vii) the costs and expenses of the Company relating to investor presentations on any “road show” undertaken in connection with the marketing of the offering of the Securities, including, without limitation, expenses associated with the preparation or dissemination of any electronic road show, expenses associated with the production of road show slides and graphics and fees, (viii) the document production charges and expenses associated with printing this Agreement and (ix) all other costs and expenses incident to the performance of the obligations of the Company hereunder for which provision is not otherwise made in this Section. It is understood, however, that except as provided in this Section, Section 8 entitled “Indemnity and Contribution,” and the last paragraph of Section 10 below, the Underwriters will pay all of their costs and expenses, including fees and disbursements of their counsel, transfer taxes payable on resale of any of the Securities by them and any advertising expenses connected with any offers they may make.

(j) During the period beginning on the date hereof and continuing to and including the Closing Date, not to offer, sell, contract to sell or otherwise dispose of any debt securities of the Company or warrants to purchase or otherwise acquire debt securities of the Company substantially similar to the Securities (other than (i) the Securities, (ii) commercial paper issued in the ordinary course of business or (iii) securities or warrants permitted with the prior written consent of the Managers).

(k) To prepare a final term sheet relating to the offering of the Securities, containing only information that describes the final terms of the Securities or the offering in a form consented to by the Managers (such consent not to be unreasonably withheld), and to file such final term sheet within the period required by Rule 433(d)(5)(ii) under the Securities Act following the date the final terms have been established for the offering of the Securities.

7. Covenants of the Underwriters. Each Underwriter severally covenants with the Company not to take any action that would result in the Company being required to file with the Commission under Rule 433(d) a free writing prospectus prepared by or on behalf of such Underwriter that otherwise would not be required to be filed by the Company thereunder, but for the action of the Underwriter.

8. Indemnity and Contribution. (a) The Company agrees to indemnify and hold harmless each Underwriter, each person, if any, who controls any Underwriter within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act, its agents and each affiliate of any Underwriter within the meaning of Rule 405 under the Securities Act from and against any and all losses, claims, damages and liabilities (including, without limitation, any legal or other expenses reasonably incurred in connection with defending or investigating any such action or claim) caused by any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement or any amendment thereof, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing prospectus as defined in Rule 433(h) under the Securities Act, any Company information that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or the Prospectus or any amendment or supplement thereto, or caused by any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except insofar as such losses, claims, damages or liabilities are caused by any such untrue statement or omission or alleged untrue statement or omission based upon information relating to any Underwriter furnished to the Company in writing by such Underwriter through you expressly for use therein.

(b) Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the Company, its directors, its officers who

signed the Registration Statement and each person, if any, who controls the Company within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act to the same extent as the foregoing indemnity from the Company to such Underwriter, but only with reference to information relating to such Underwriter furnished to the Company in writing by such Underwriter through you expressly for use in the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing prospectus or the Prospectus or any amendment or supplement thereto.

(c) In case any proceeding (including any governmental investigation) shall be instituted involving any person in respect of which indemnity may be sought pursuant to Section 8(a) or 8(b), such person (the “indemnified party”) shall promptly notify the person against whom such indemnity may be sought (the “indemnifying party”) in writing and the indemnifying party, upon request of the indemnified party, shall retain counsel reasonably satisfactory to the indemnified party to represent the indemnified party and any others the indemnifying party may designate in such proceeding and shall pay the fees and disbursements of such counsel related to such proceeding. In any such proceeding, any indemnified party shall have the right to retain its own counsel, but the fees and expenses of such counsel shall be at the expense of such indemnified party unless (i) the indemnifying party and the indemnified party shall have mutually agreed to the retention of such counsel or (ii) the named parties to any such proceeding (including any impleaded parties) include both the indemnifying party and the indemnified party and representation of both parties by the same counsel would be inappropriate due to actual or potential differing interests between them. It is understood that the indemnifying party shall not, in respect of the legal expenses of any indemnified party in connection with any proceeding or related proceedings in the same jurisdiction, be liable for the fees and expenses of more than one separate firm (in addition to any local counsel) for all such indemnified parties and that all such fees and expenses shall be reimbursed as they are incurred. Such firm shall be designated in writing by the Managers, in the case of parties indemnified pursuant to Section 8(a), and by the Company, in the case of parties indemnified pursuant to Section 8(b). The indemnifying party shall not be liable for any settlement of any proceeding effected without its written consent, but if settled with such consent or if there be a final judgment for the plaintiff, the indemnifying party agrees to indemnify the indemnified party from and against any loss or liability by reason of such settlement or judgment. Notwithstanding the foregoing sentence, if at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel as contemplated by the second and third sentences of this paragraph, the indemnifying party agrees that it shall be liable for any settlement of any proceeding effected without its written consent if (i) such settlement is entered into more than

30 days after receipt by such indemnifying party of the aforesaid request and (ii) such indemnifying party shall not have reimbursed the indemnified party in accordance with such request prior to the date of such settlement. No indemnifying party shall, without the prior written consent of the indemnified party, effect any settlement of any pending or threatened proceeding in respect of which any indemnified party is or could have been a party and indemnity could have been sought hereunder by such indemnified party, unless such settlement (x) includes an unconditional release of such indemnified party from all liability on claims that are the subject matter of such proceeding and (y) does not include any statement as to fault, culpability or a failure to act by or on behalf of any indemnified party.

(d) To the extent the indemnification provided for in Section 8(a) or 8(b) is unavailable to an indemnified party or insufficient in respect of any losses, claims, damages or liabilities referred to therein, then each indemnifying party under such paragraph, in lieu of indemnifying such indemnified party thereunder, shall contribute to the amount paid or payable by such indemnified party as a result of such losses, claims, damages or liabilities (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the offering of the Securities or (ii) if the allocation provided by clause 8(d)(i) above is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause 8(d)(i) above but also the relative fault of the Company on the one hand and of the Underwriters on the other hand in connection with the statements or omissions that resulted in such losses, claims, damages or liabilities, as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriters on the other hand in connection with the offering of the Securities shall be deemed to be in the same respective proportions as the net proceeds from the offering of the Securities (before deducting expenses) received by the Company and the total underwriting discounts and commissions received by the Underwriters bear to the aggregate initial public offering price of the Securities as set forth in the Prospectus. The relative fault of the Company on the one hand and the Underwriters on the other hand shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company or by the Underwriters and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission. The Underwriters’ respective obligations to contribute pursuant to this Section 8 are several in proportion to the respective principal amounts of Securities they have purchased hereunder, and not joint.

(e) The Company and the Underwriters agree that it would not be just or equitable if contribution pursuant to this Section 8 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation that does not take account of the equitable considerations referred to in Section 8(d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages and liabilities referred to in Section 8(d) shall be deemed to include, subject to the limitations set forth above, any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 8, no Underwriter shall be required to contribute any amount in excess of the amount by which the total underwriting discounts and commissions received by such Underwriter with respect to the sale of the Securities exceeds the amount of any damages that such Underwriter has otherwise been required to pay by reason of such untrue or alleged untrue statement or omission or alleged omission. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. The remedies provided for in this Section 8 are not exclusive and shall not limit any rights or remedies which may otherwise be available to any indemnified party at law or in equity.

(f) The indemnity and contribution provisions contained in this Section 8 and the representations, warranties and other statements of the Company contained in this Agreement shall remain operative and in full force and effect regardless of (i) any termination of this Agreement, (ii) any investigation made by or on behalf of any Underwriter, any person controlling any Underwriter or any affiliate of any Underwriter or by or on behalf of the Company, its officers or directors or any person controlling the Company and (iii) acceptance of and payment for any of the Securities.

9. Termination. The Underwriters may terminate this Agreement by notice given by you to the Company, if after the execution and delivery of this Agreement and prior to the Closing Date (i) trading generally shall have been suspended or materially limited on, or by, as the case may be, any of the New York Stock Exchange (including the New York Stock Exchange LLC), the NASDAQ Global Market, the Chicago Board of Options Exchange, the Chicago Mercantile Exchange or the Chicago Board of Trade, (ii) trading of any securities of the Company shall have been suspended on any exchange or in any over-the-counter market, (iii) a material disruption in securities settlement, payment or clearance services in the United States shall have occurred, (iv) any moratorium on commercial banking activities shall have been declared by Federal or New York State authorities or (v) there shall have occurred any outbreak or escalation of hostilities, or any change in financial markets or any calamity or

crisis that, in your judgment, is material and adverse and which, singly or together with any other event specified in this clause (v), makes it, in your judgment, impracticable or inadvisable to proceed with the offer, sale or delivery of the Securities on the terms and in the manner contemplated in the Time of Sale Prospectus or the Prospectus.

10. Effectiveness; Defaulting Underwriters. This Agreement shall become effective upon the execution and delivery hereof by the parties hereto.

If, on the Closing Date, any one or more of the Underwriters shall fail or refuse to purchase Securities that it has or they have agreed to purchase hereunder on such date, and the aggregate principal amount of Securities which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase is not more than one-tenth of the aggregate principal amount of the Securities to be purchased on such date, the other Underwriters shall be obligated severally in the proportions that the principal amount of Securities set forth opposite their respective names in Schedule II bears to the aggregate principal amount of Securities set forth opposite the names of all such non-defaulting Underwriters, or in such other proportions as you may specify, to purchase the Securities which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase on such date; provided that in no event shall the principal amount of Securities that any Underwriter has agreed to purchase pursuant to this Agreement be increased pursuant to this Section 10 by an amount in excess of one-ninth of such principal amount of Securities without the written consent of such Underwriter. If, on the Closing Date, any Underwriter or Underwriters shall fail or refuse to purchase Securities and the aggregate principal amount of Securities with respect to which such default occurs is more than one-tenth of the aggregate principal amount of Securities to be purchased on such date, and arrangements satisfactory to you and the Company for the purchase of such Securities are not made within 36 hours after such default, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter or the Company. In any such case either you or the Company shall have the right to postpone the Closing Date, but in no event for longer than seven days, in order that the required changes, if any, in the Registration Statement, in the Time of Sale Prospectus, in the Prospectus or in any other documents or arrangements may be effected. Any action taken under this paragraph shall not relieve any defaulting Underwriter from liability in respect of any default of such Underwriter under this Agreement.

If this Agreement shall be terminated by the Underwriters, or any of them, because of any failure or refusal on the part of the Company to comply with the terms or to fulfill any of the conditions of this Agreement, or if for any reason the Company shall be unable to perform its obligations under this Agreement (other than in any event for which such failure to perform by the Company was a direct result of a failure to perform by the Underwriters under this Agreement), the Company will reimburse the Underwriters or such Underwriters as have so terminated this Agreement with respect to themselves, severally, for all out-of-pocket expenses (including the fees and disbursements of their counsel)

reasonably incurred by such Underwriters in connection with this Agreement or the offering contemplated hereunder.

11. Entire Agreement. (a) This Agreement, together with any contemporaneous written agreements and any prior written agreements (to the extent not superseded by this Agreement) that relate to the offering of the Securities, represents the entire agreement between the Company and the Underwriters with respect to the preparation of any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, the conduct of the offering, and the purchase and sale of the Securities.

(b) The Company acknowledges that in connection with the offering of the Securities: (i) the Underwriters have acted at arms length, are not agents of, and owe no fiduciary duties to, the Company or any other person, (ii) the Underwriters owe the Company only those duties and obligations set forth in this Agreement and prior written agreements (to the extent not superseded by this Agreement), if any, and (iii) the Underwriters may have interests that differ from those of the Company. The Company waives to the full extent permitted by applicable law any claims it may have against the Underwriters arising from an alleged breach of fiduciary duty in connection with the offering of the Securities.

12. Counterparts. This Agreement may be signed in two or more counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument.

13. Applicable Law. This Agreement shall be governed by and construed in accordance with the internal laws of the State of New York.

14. Headings. The headings of the sections of this Agreement have been inserted for convenience of reference only and shall not be deemed a part of this Agreement.

15. Notices. All communications hereunder shall be in writing and effective only upon receipt and if to the Underwriters shall be delivered, mailed or sent to you at the address set forth in Schedule I hereto; and if to the Company shall be delivered, mailed or sent to the address set forth in Schedule I hereto.


Very truly yours,

JUNIPER NETWORKS, INC.

By:		/s/ Xxxxxxxx Xxxxxx
		Name: Xxxxxxxx Xxxxxx
		Title: Executive Vice President

[Signature page to Underwriting Agreement]

Accepted as of the date hereof

BARCLAYS CAPITAL INC.

CITIGROUP GLOBAL MARKETS INC.

XXXXXX XXXXXXX & CO. INCORPORATED

Acting severally on behalf of themselves and the several

Underwriters named in Schedule II hereto


By:		BARCLAYS CAPITAL INC.

By:		/s/ Xxxxxx Xxxxx
		Name: /s/ Xxxxxx Xxxxx
		Title: Managing Director

By:		CITIGROUP GLOBAL MARKETS INC.

By:		/s/ Xxxxx Xxxxxxxxx
		Name: Xxxxx Xxxxxxxxx
		Title: Managing Director

By:		XXXXXX XXXXXXX & CO. INCORPORATED

By:		/s/ Yurij Slyz
		Name: Yurij Slyz
		Title: Executive Director

SCHEDULE I


Managers:		Barclays Capital Inc. Citigroup Global Markets Inc. Xxxxxx Xxxxxxx & Co. Incorporated

Trustee:		The Bank of New York Mellon Trust Company, N.A.

Registration Statement File No.:		333-168733

Time of Sale Prospectus		1. Preliminary Prospectus dated February 28, 2011 relating to the Securities 2. Free Writing Prospectus dated February 28, 2011 relating to the 2016 Notes (as defined) 3. Free Writing Prospectus dated February 28, 2011 relating to the 2021 Notes (as defined) 4. Free Writing Prospectus dated February 28, 2011 relating to the 2041 Notes (as defined)

Closing Date and Time:		March 3, 2011 10:00 a.m. EST

Closing Location:		Xxxxxx Xxxxxxx Xxxxxxxx & Xxxxxx, Professional Corporation 000 Xxxx Xxxx Xxxx Xxxx Xxxx, XX 00000

Address for Notices to Underwriters:		Barclays Capital Inc. 000 Xxxxxxx Xxxxxx Xxx Xxxx, XX 00000 Attention.: Syndicate Registration Facsimile: (000) 000-0000 Citigroup Global Markets Inc. 000 Xxxxxxxxx Xx. Xxx Xxxx, XX 00000 Attention: General Counsel Facsimile: (000) 000-0000

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		Xxxxxx Xxxxxxx & Co. Incorporated 0000 Xxxxxxxx, 00xx Xxxxx Xxx Xxxx, XX 00000 Attention: Investment Banking Division Phone: (000) 000-0000 Facsimile: (000) 000-0000

Address for Notices to the Company:		Juniper Networks, Inc. 0000 Xxxxx Xxxxxxxx Xxxxxx Xxxxxxxxx, XX 00000 Attention: General Counsel Facsimile: (000) 000-0000 With a copy to: Xxxxxx Xxxxxxx Xxxxxxxx & Xxxxxx, Professional Corporation 000 Xxxx Xxxx Xxxx Xxxx Xxxx, XX 00000 Attention: Xxxxxxxxx X. Xxxxxx, Esq. Facsimile: (000) 000-0000

Securities:		The 2016 Notes, the 2021 Notes and the 2041 Notes

2016 Notes

Securities to be purchased:		3.100% Senior Notes due 2016 (the “2016 Notes”)

Aggregate Principal Amount:		$300,000,000

Purchase Price:		99.478% of the principal amount of the Securities, plus accrued interest, if any, from March 3, 2011

Maturity:		March 15, 2016

Interest Rate:		3.100% per annum, accruing from March 3, 2011

Interest Payment Dates:		September 15 and March 15, commencing September 15, 2011

Make-Whole Spread:		Treasury plus 15 basis points

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2021 Notes

Securities to be purchased:		4.600% Senior Notes due 2021 (the “2021 Notes”)

Aggregate Principal Amount:		$300,000,000

Purchase Price:		99.421% of the principal amount of the Securities, plus accrued interest, if any, from March 3, 2011

Maturity:		March 15, 2021

Interest Rate:		4.600% per annum, accruing from March 3, 2011

Interest Payment Dates:		September 15 and March 15, commencing September 15, 2011

Make-Whole Spread:		Treasury plus 20 basis points

2041 Notes

Securities to be purchased:		5.950% Senior Notes due 2041 (the “2041 Notes”)

Aggregate Principal Amount:		$400,000,000

Purchase Price:		99.080% of the principal amount of the Securities, plus accrued interest, if any, from March 3, 2011

Maturity:		March 15, 2041

Interest Rate:		5.950% per annum, accruing from March 3, 2011

Interest Payment Dates:		September 15 and March 15 commencing September 15, 2011

Make-Whole Spread:		Treasury plus 25 basis points

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SCHEDULE II


Underwriter	Principal Amount of 2016 Notes to be Purchased		Principal Amount of 2021 Notes to be Purchased		Principal Amount of 2041 Notes to be Purchased
BARCLAYS CAPITAL INC.	$	100,000,000	$	100,000,000	$	133,334,000
CITIGROUP GLOBAL MARKETS INC.		100,000,000		100,000,000		133,333,000
XXXXXX XXXXXXX & CO. INCORPORATED		100,000,000		100,000,000		133,333,000

Total	$	300,000,000	$	300,000,000	$	400,000,000

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ANNEX A

FORM OF OPINION OF OUTSIDE COUNSEL

The Registration Statement is effective under the Securities Act. The Prospectus was filed with the Commission pursuant to Rule 424(b)(5) under the Securities Act on , 2011.

To our knowledge, no order suspending the effectiveness of the Registration Statement has been issued, no notice of objection of the Commission to the use of such registration statement or any post-effective amendment thereto pursuant to Rule 401(g)(2) under the Securities Act has been received by the Company.

The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Delaware, with corporate power and authority to own, lease and operate its properties and conduct its business as described in the Registration Statement, the Pricing Disclosure Package and the Prospectus.

The Company is duly qualified to do business as a foreign corporation in good standing in the State of California.

Each of the Base Indenture and the Supplemental Indenture has been duly authorized, executed and delivered by the Company and constitutes a valid and binding agreement of the Company, enforceable against the Company in accordance with its terms.

The Notes have been duly authorized, executed and delivered by the Company and, when duly authenticated as provided in the Indenture and paid for as provided in the Underwriting Agreement, will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms, and will be entitled to the benefits of the Indenture.

The Underwriting Agreement has been duly authorized, executed and delivered by the Company.

The statements set forth in (A) the Registration Statement in Item 15 and (B) the Pricing Disclosure Package and the Prospectus under the captions “Description of the Notes,” “Description of the Debt Securities,” and “Underwriting,” insofar as such statements constitute summaries of the legal matters, documents or proceedings set forth therein, fairly summarize in all material respects the matters referred to therein.

Schedule A

The issuance and sale of the Notes being delivered on the date hereof, and the execution, delivery and performance by the Company of its obligations under the Transaction Documents, and the consummation of the transactions contemplated by the Transaction Documents do not conflict with or result in a breach or violation by the Company of any of the terms or provisions of, or constitute a default under, any Reviewed Agreement, nor will such action result in any violation by the Company of (i) its Certificate of Incorporation or the Bylaws, (ii) any U.S. federal, California, New York or Delaware (under the DGCL) state statute, or (iii) any Reviewed Judgment, in the case of clause (ii) above, having jurisdiction over the Company or any of its properties.

10.

No consent, approval, authorization or order of, or filing with, any U.S. federal, California, New York or Delaware (solely with respect to the DGCL) governmental agency or body or any court is required for the execution, delivery and performance by the Company of the Transaction Documents, the compliance by the Company with the terms thereof, the issuance and sale of the Notes being delivered on the Closing Date, and the consummation of the transactions contemplated by the Transaction Documents or the Pricing Disclosure Package and the Prospectus, except such as may be required under state securities laws or Blue Sky laws and except as may be contemplated by the Transaction Documents.

11.

The Company is not and, after giving effect to the offering and sale of the Notes and the application of the proceeds thereof as described in the Registration Statement, the Pricing Disclosure Package and the Prospectus, will not be required to register as an “investment company” within the meaning of the Investment Company Act.

12.

The statements set forth in the Pricing Disclosure Package and the Prospectus under the caption “Material U.S. Federal Income Tax Considerations,” insofar as they constitute summaries of legal matters or conclusions with respect thereto, fairly summarize the matters referred to therein in all material respects.

We have participated in conferences with representatives of the Company, the Underwriters and counsel for the Underwriters and with representatives of the Company’s independent accountants and counsel, at which conferences the contents of the Registration Statement, the Pricing Disclosure Package and the Prospectus and any amendment and supplement thereto and related matters were discussed and, although we assume no responsibility for the accuracy, completeness or fairness of the Registration Statement, the Pricing Disclosure Package, the Prospectus and any

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amendment or supplement thereto (except as expressly provided in paragraphs 8 and 12 above), nothing has come to our attention to cause us to believe that:

(A)

the Registration Statement, at the time each part became effective, contained any untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading (other than the financial statements and related schedules and the financial and statistical data based on or derived from such financial statements or schedules or schedules included or incorporated by reference therein or omitted therefrom, as to which we express no comment);

(B)

the Pricing Disclosure Package, all considered together as of the Applicable Time (which we assume to be 4:00 p.m. PST on February 28, 2011) and the Closing Date, contained any untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading (other than the financial statements and related schedules and the financial and statistical data derived from such financial statements or schedules or schedules included or incorporated by reference therein or omitted therefrom, as to which we express no comment); or

(C)

the Prospectus as of its date and the Closing Date contains any untrue statement of a material fact or omits to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading (other than the financial statements and related schedules and the financial and statistical data based on or derived from such financial statements or schedules or schedules included or incorporated by reference therein or omitted therefrom, as to which we express no comment).

To our knowledge, except as described in the Registration Statement, the Pricing Disclosure Package and the Prospectus, there are no legal, governmental or regulatory investigations, actions, suits or proceedings pending to which the Company or any of its subsidiaries is or may be a party or to which any property of the Company or any of its subsidiaries is or may be the subject that are required to be described in the Registration Statement, the Pricing Disclosure Package and the Prospectus and are not so described. In expressing this opinion, we have not conducted a docket search in any jurisdiction with respect to any litigation that may be pending against the Company or any of its subsidiaries.

The Registration Statement, the Preliminary Prospectus, and the Prospectus (other than the financial statements and related schedules and the financial and statistical data based on or derived from such financial statements or schedules or schedules included or incorporated by reference therein, as to which we express no comment) are, on their face, appropriately responsive, in all

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material respects, to the requirements of the Securities Act. For purposes of this paragraph, we have assumed that the statements made in the Registration Statement, the Preliminary Prospectus and the Prospectus are correct and complete.

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JUNIPER NETWORKS, INC. 3.100% Senior Notes due 2016 4.600% Senior Notes due 2021 5.950% Senior Notes due 2041 UNDERWRITING AGREEMENT

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