Document:

<PAGE>

                                                                     EXHIBIT 4.1

                   [LOGO OF VIA NET.WORKS, INC. APPEARS HERE]

COMMON STOCK                                                   COMMON STOCK
   NUMBER                                                         SHARES

                              VIA NET.WORKS, INC.

    SEE REVERSE FOR CERTAIN DEFINITIONS                       CUSIP 925912 10 7
AND STATEMENTS AS TO THE RIGHTS. PREFERENCES,
   PRIVILEGES AND RESTRICTIONS ON SHARES

             INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

   This certifies that

is the owner of

fully paid and non-assessable shares of common stock, par value $.001 per share
of

                              VIA NET.WORKS, INC.
                  (the "Corporation"), a Delaware Corporation

     The shares represented by this certificate are transferable only on the
stock transfer books of the Corporation by the holder of record hereof or by
duly authorized attorney upon the surrender of this certificate properly
endorsed. This certificate is not valid until countersigned and registered by
the Corporation's Transfer agent and Registrar.

     IN WITNESS WHEREOF, the Corporation has caused this certificate to be
executed by the facsimile signatures of its duly authorized officers and has
caused a facsimile of its corporate seal to be hereunto affixed.

Dated:

                   [SEAL OF VIA NET.WORKS, INC. APPEARS HERE]

     SECRETARY                                                 PRESIDENT

COUNTERSIGNED AND REGISTERED

                                                                  TRANSFER AGENT
                                                                   AND REGISTRAR

BY
                                                            AUTHORIZED SIGNATURE

<PAGE>

     The corporation is authorized to issue more than one class or series of
stock. The Corporation will furnish without charge to each stockholder who so
requests a statement of the powers, designations, preferences and relative,
participating, optional or other special rights of each class of stock or series
thereof and the qualifications, limitations or restrictions of such preferences
and/or rights. Such request may be made to the Secretary of the Company.

     The following abbreviations, when used in the inscription on the face of
each certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

     TEN COM  -  as tenants in common
     TEN ENT  -  as tenants by the entireties
     JT TEN   -  as joint tenants with right
                 of survivorship and not as
                 tenants in common

      UNIF TRANSFER MIN ACT -                      Custodian
                              --------------------           -------------------
                                    (Cust)                         (Minor)

                              under Uniform Transfers to Minors
                              Act
                                 -----------------------------------
                                              (State)

     Additional abbreviations may also be used though not in the above list

     For value received, ___________________________________hereby sell(s),
assign(s) and transfer(s) unto

   PLEASE INSERT SOCIAL SECURITY OR OTHER
       IDENTIFYING NUMBER OF ASSIGNEE

--------------------------------------------

--------------------------------------------

--------------------------------------------------------------------------------
  (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS INCLUDING ZIP CODE OF ASSIGNEE)

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
                                                                      Shares
---------------------------------------------------------------------
of the common stock evidenced by this certificate, and do (does) hereby
irrevocably constitute and appoint
                                                                   , Attorney,
-------------------------------------------------------------------
to transfer the said shares on the books of the Corporation, with full power of
substitution in the premises.

Dated
     -------------------------                   -------------------------------
                                                 Signature

                                                 -------------------------------
                                                 Signature

In presence of
              ---------------------------

NOTE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME OF THE
STOCKHOLDER(S) AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR,
WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.<PAGE>

                                                                    EXHIBIT 10.4

                               PURCHASE AGREEMENT

          THIS PURCHASE AGREEMENT, dated as of February __, 2000, (the
"Agreement"), is entered into between VIA NET.WORKS, Inc., a Delaware
corporation (the "Company"), and each of those persons and entities whose names
are set forth on Schedule I attached hereto (collectively, the "Purchasers" and
                 ----------
individually, a "Purchaser").

          WHEREAS, the Company and the Purchasers, who are currently holders of
the Company's Series A, B-1 and C-1 voting mandatorily redeemable convertible
preferred stock and Series B-2 and C-2 nonvoting mandatorily redeemable
convertible preferred stock (collectively, the "Preferred Stock"), are parties
to that certain Amended and Restated Stockholders Agreement, dated as of April
20, 1999 (the "Stockholders Agreement");

          WHEREAS, pursuant to Section 4.11 of the Stockholders Agreement, the
Company and the Purchasers have agreed that, in connection with the Company's
initial public offering, the Company would set aside not less than 5% of the
securities proposed to be offered to the public for purchase by the Purchasers;

          WHEREAS, the Company has filed with the Securities and Exchange
Commission (the "Commission") a registration statement on Form S-1 and
amendments thereto (No. 333-91615) (the "Registration Statement") under the
Securities Act of 1933, as amended, and the rules and regulations of the
Commission thereunder (collectively, the "Act"); and

          WHEREAS, the Company intends to effect an initial public offering (the
"IPO") of up to 14,000,000 shares (the "Shares") of its common stock, par value
$.001 per share (the "Common Stock"), 5%, or 700,000 Shares, of which are being
offered to the Purchasers (the "Reserved Shares") pursuant to, and in compliance
with, Section 4.11 of the Stockholders Agreement (the "Reserved Share
Offering").

          NOW, THEREFORE, for and in consideration of the premises, and for
other good and valuable consideration, the receipt and sufficiency of which is
hereby acknowledged, the parties hereto agree as follows:

                                   ARTICLE I
                     REGISTRATION STATEMENT AND PROSPECTUS

          Section 1.1  Registration Statement.  The Company has prepared and
                       ----------------------
filed with the Commission, in accordance with the provisions of the Act, the
Registration Statement.  The Registration Statement contains two prospectuses:
(i) the U.S. prospectus (the "U.S. Prospectus") to be used in connection with
the offer and sale of up to 13,300,000 Shares in the United States and Canada
and the resale of a portion of such Shares into the United States during the
period after the date hereof in which the Underwriters (as defined herein) are
required to deliver a prospectus under the Act and (ii) a separate prospectus to
<PAGE>

be used in connection with the Reserved Share Offering (the "Reserved Share
Prospectus").  In connection with the offer and sale of the Reserved Shares, the
Company has prepared a preliminary Reserved Share Prospectus to be used in
connection with the Reserved Share Offering and the final Reserved Share
Prospectus.  It is understood that the preliminary Reserved Share Prospectus and
the Reserved Share Prospectus will be identical to the preliminary U.S.
Prospectus and the U.S. Prospectus, respectively, except for certain substitute
pages.

          The Registration Statement, as amended at the time it became
effective, shall include the information (if any) deemed to be part of the
Registration Statement at the time of effectiveness pursuant to Rule 430A under
the Act.  The U.S. Prospectus and the Reserved Shares Prospectus in the
respective forms first used to confirm sales of Shares are hereinafter
collectively referred to as the "Prospectus."  If the Company has filed or is
required pursuant to the terms hereof to file a registration statement pursuant
to Rule 462(b) under the Act registering additional shares of Common Stock (a
"Rule 462(b) Registration Statement"), then, unless otherwise specified, any
reference herein to the term "Registration Statement" shall be deemed to include
such Rule 462(b) Registration Statement.  The Company agrees that the shares
issued in the Reserved Share Offering will be sold to the Purchasers at the
initial public offering price listed on the cover page of the Prospectus.

                                   ARTICLE II
                               PURCHASE AND SALE

          Section 2.1  Purchase and Sale.  On the basis of the representations
                       -----------------
and warranties contained in this Agreement, and subject to its terms and
conditions, the Company agrees to issue and sell, and each Purchaser agrees,
severally and not jointly, to purchase from the Company at a price per Share of
$______ (the "Purchase Price"), which Purchase Price represents the price per
Share offered to the public pursuant to the IPO as set forth on the cover page
of the Prospectus, the number of the Shares set forth opposite the name of such
Purchaser in Schedule I attached hereto.
             ----------

          Section 2.2  Power of Attorney.  Each Purchaser shall execute and
                       -----------------
deliver to the Company a power of attorney substantially in the form attached
hereto as Exhibit A (the "Power of Attorney") appointing and designating
          ---------
Catherine A. Graham and Matt S. Nydell as attorneys-in-fact to the extent set
forth therein, relating to the transactions contemplated hereby.

          Section 2.3  Lock-Up Agreements.  Prior to, or concurrently with, the
                       ------------------
execution of this Agreement, each of the Purchasers shall have executed, or will
execute, and deliver to the Company a lock-up agreement (the "Lock-Up
Agreements") referred to in the Underwriting Agreement (as defined herein).  The
Reserved Shares offered herewith and any securities owned by the Purchasers that
are convertible into or exercisable or exchangeable for Common Stock, including
the Preferred Stock, shall be subject to the Lock-Up Agreements.

                                       2
<PAGE>

          Section 2.4  Delivery and Payment.  The Reserved Shares shall be
                       --------------------
represented by definitive certificates and shall be issued and delivered to the
Purchasers in authorized denominations and amounts on or before the Closing Date
(as defined herein), against payment on the Closing Date of the Purchase Price
therefor by wire transfer of immediately available funds or by bank cashier's
check. The time and date of delivery and payment for the Reserved Shares shall
be 9:00 A.M., New York City time, on February __, 2000, or such other time on
the same or such other date as the Company and the Purchasers shall agree in
writing and the delivery and payment shall take place at the law offices of
Hogan & Hartson L.L.P., 555 Thirteenth Street, N.W., Washington, D.C. 20004-
1109, or such other place as the Company and the Purchasers shall agree in
writing.

                                  ARTICLE III
                         REPRESENTATIONS AND WARRANTIES

          Section 3.1  Representations and Warranties of the Company. The
                       ---------------------------------------------
Company represents and warrants to each Purchaser that:

          (a) The Registration Statement has become effective (other than any
Rule 462(b) Registration Statement to be filed by the Company after the
effectiveness of this Agreement); any Rule 462(b) Registration Statement filed
after the effectiveness of this Agreement will become effective no later than
10:00 P.M., New York City time, on the date of this Agreement; and no stop order
suspending the effectiveness of the Registration Statement is in effect, and, to
the Company's knowledge, no proceedings for such purpose are pending before or
threatened by the Commission.

          (b) (i) The Registration Statement (other than any Rule 462(b)
Registration Statement to be filed by the Company after the effectiveness of
this Agreement), when it became effective, did not contain and, as amended, 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, (ii) the Registration Statement (other than
any Rule 462(b) Registration Statement to be filed by the Company after the
effectiveness of this Agreement) and the Prospectus comply and, as amended or
supplemented, if applicable, will comply in all material respects with the Act,
(iii) if the Company is required to file a Rule 462(b) Registration Statement
after the effectiveness of this Agreement, such Rule 462(b) Registration
Statement and any amendments thereto, when they become effective (A) 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 and (B) will comply in all material respects with the Act and (iv)
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
statements or omissions in the Registration Statement, any Rule 462(b)
Registration Statement or the Prospectus, as amended or supplemented, based upon
information furnished to the Company in writing by or on behalf of any
underwriter or underwriters expressly for use therein.

                                       3
<PAGE>

          (c) The Company is a corporation that is duly organized, validly
existing and in good standing under the laws of the State of Delaware and has
the power and authority under its charter and the laws of the State of Delaware
to carry on its business as described in the Prospectus and to own, lease and
operate its properties, and the Company is duly qualified and is in good
standing, as a foreign entity authorized to do business in each jurisdiction in
which the nature of its business or its ownership or leasing of property
requires such qualification, except where the failure to be so qualified would
not have a material adverse effect on the business, financial condition or
results of operations of the Company and its subsidiaries, taken as a whole.

          (d)  All the outstanding shares of capital stock of the Company have
been duly authorized and validly issued and are fully paid, non-assessable and
not issued in violation of any preemptive or similar rights; and the Reserved
Shares to be issued and sold by the Company hereunder have been duly authorized
and, when issued and delivered to the Purchasers against payment therefor as
provided by this Agreement, will be validly issued, fully paid and non-
assessable, and, except as disclosed in the Registration Statement, the issuance
of such Reserved Shares will not be subject to any preemptive or similar rights.

          (e)  The authorized capital stock of the Company conforms in all
material respects as to legal matters to the description thereof contained in
the Prospectus.

          (f)  The Company is not (x) in violation of its charter or by-laws or
(y) in default in the performance of any obligation, agreement, covenant or
condition contained in any indenture, loan agreement, mortgage, lease or other
agreement or instrument to which the Company is a party or by which the Company
or its property is bound, except, with respect to clause (y), for any such
violation or default that would not have a material adverse effect on the
business, financial condition or results of operations of the Company and its
subsidiaries taken as a whole.

          (g)  The execution, delivery and performance of this Agreement by the
Company, the compliance by the Company with all the provisions hereof and the
consummation of the transactions contemplated hereby and the application of the
net proceeds from the sale of the Reserved Shares as contemplated by the
Registration Statement will not (i) require any consent, approval, authorization
or other order of, or qualification with, any court or governmental body or
agency (except as has been obtained and except as may be required under the
securities or Blue Sky laws of the various states), (ii) conflict with, or
constitute a breach of any of the terms or provisions of, or a default under (or
event which, with giving of notice or lapse of time or both, would be a default
under) or result in the creation or imposition of any lien, charge or
encumbrance upon any property or assets of the Company to, (A) the charter or
by-laws of the Company or (B) any indenture, loan agreement, mortgage, lease or
other agreement or instrument that is material to the Company, to which the
Company is a party or by which the Company or its property is bound, or (iii)
violate or conflict with any applicable law or any rule, regulation, judgment,
order or decree of any court or any governmental body or agency having
jurisdiction over the Company or its property or, except where such failure to
be valid and in full force and effect or to be in compliance, the occurrence of
any such event or the presence of any such restriction would not, individually
or in the aggregate, have a material

                                       4
<PAGE>

adverse effect on the business, prospects, financial condition or results of
operations of the Company and its subsidiaries taken as a whole.

          (h)  There are no legal or governmental proceedings pending or
threatened to which the Company is or, to the knowledge of the Company, is
reasonably expected to be a party or to which any of its property is or, to the
knowledge of the Company, is reasonably expected to be subject, that are
required to be described in the Registration Statement or the Prospectus and are
not so described; nor are there any 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
so described or filed.

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

          (j)  Since the respective dates as of which information is given in
the Prospectus other than as set forth in the Prospectus (exclusive of any
amendments or supplements thereto subsequent to the date of this Agreement), (i)
there has not occurred any material adverse change or any development involving
a prospective material adverse change in the condition, financial or otherwise,
or the earnings, business, management or operations of the Company and its
subsidiaries, taken as a whole, (ii) there has not been any material adverse
change or any development involving a prospective material adverse change in the
capital stock or in the long-term debt of the Company and any of its
subsidiaries, taken as a whole, (iii) the Company has not incurred any liability
or obligation, direct or contingent, that is material to the Company and its
subsidiaries, taken as a whole, and (iv) there has been no dividend or
distribution of any kind declared, paid or made by the Company or, except for
dividends paid to the Company or other subsidiaries, any of its subsidiaries on
any class of capital stock or repurchase or redemption by the Company or any of
its subsidiaries of any class of capital stock.

          (k) There are no contracts or documents that are required to be
described in the Registration Statement or to be filed as exhibits thereto which
have not been so described or filed as required.

          (l) No vote or consent of any stockholder of the Company, and no
consent, approval or waiver of any party to or any person entitled to any right
or benefit under the charter or by-laws of the Company, any stockholders'
agreements or arrangements, or any other instrument or agreement to which the
Company is a party or by which it is bound or under which it is entitled to any
right or benefit, except such consents, approvals or waivers which have been
obtained, is required in connection with the offering, issuance, sale or
purchase by you of any of the Reserved Shares under this Agreement or the
consummation of any of the other transactions contemplated hereby or the
application of the net proceeds from the sale of the Shares as contemplated by
the Registration Statement.

          Section 3.2  Representations and Warranties of the Purchasers. Each of
                       ------------------------------------------------
the Purchasers represents and warrants to the Company that:

          (a) Such Purchaser has all necessary power and authority under all
applicable provisions of law to execute, deliver and perform its obligations
under this

                                       5
<PAGE>

Agreement and the Power of Attorney and to carry out their respective
provisions. The execution, delivery and performance of this Agreement and the
Power of Attorney by the Purchaser, the compliance by the Purchaser with all the
provisions hereof and thereof and the consummation of the transactions
contemplated hereby and thereby will not (i) require any consent, approval,
authorization or other order of, or qualification with, any court or
governmental body or agency, (ii) conflict with, or constitute a breach of any
of the terms or provisions of, or a default under organizational or governing
documents of the Purchaser, or (iii) violate or conflict with any applicable law
or any rule, regulation, judgment, order or decree of any court or any
governmental body or agency having jurisdiction over the Purchaser. All actions
on such Purchaser's part required for the lawful execution and delivery of this
Agreement and the Power of Attorney have been or will be effectively taken prior
to the Closing.

          (b) This Agreement and the Power of Attorney constitute valid and
binding obligations of such Purchaser, enforceable in accordance with their
terms, except (i) as may be limited by bankruptcy, insolvency, reorganization,
moratorium or other laws affecting creditors' rights (including, without
limitation, the effect of statutory and other law regarding fraudulent
conveyances, fraudulent transfers and preferential transfers) and (ii) as may be
limited by the exercise of judicial discretion and the application of principles
of equity including, without limitation, requirements of good faith, fair
dealing, conscionability and materiality (regardless of whether such agreements
are considered in a proceeding at equity or at law).

          (c) Such Purchaser acknowledges and agrees that the Reserved Shares
shall be subject to certain trading restrictions as more fully set forth in the
Lock-Up Agreements.

          (d) Such Purchaser acknowledges and agrees that the sale and offer of
the Reserved Shares being made hereunder by the Company fully complies with, and
satisfies the Company's obligation under, the Stockholders Agreement and that
the Company is not in violation of any provision of the Stockholders Agreement.

          (e) Such Purchaser is acquiring the Reserved Shares for its own
account.

                                   ARTICLE IV
                        CONDITIONS PRECEDENT TO CLOSING

          Section 4.1  Conditions to each Purchaser's Obligations.  The
                       ------------------------------------------
obligation of each Purchaser to purchase and pay for the Reserved Shares to be
delivered at the Closing shall be subject to the satisfaction of the following
conditions as of the Closing Date:

          (i)    All the representations and warranties of the Company contained
in this Agreement shall be true and correct on the Closing Date with the same
force and effect as if made on and as of the Closing Date;

          (ii)   If the Company is required to file a Rule 462(b) Registration
Statement after the effectiveness of this Agreement, such Rule 462(b)
Registration

                                       6
<PAGE>

Statement shall have become effective by 10:00 P.M., New York City
time, on the date of this Agreement; and no stop order suspending the
effectiveness of the Registration Statement shall have been issued and no
proceedings for that purpose shall have been commenced or shall be pending
before or contemplated by the Commission; and

          (iii)  the Underwriters shall have purchased the Shares from the
Company pursuant to that certain Underwriting Agreement (the "Underwriting
Agreement") by and among the Company and Donaldson, Lufkin & Jenrette Securities
Corporation, Morgan Stanley & Co. Incorporated, Salomon Smith Barney Inc. and
DLJdirect, as representatives of the several underwriters, and Donaldson, Lufkin
& Jenrette International, Morgan Stanley & Co. International Limited, Salomon
Brothers International Limited, Cazenove & Co. and Mees Pierson N.V., as
Representatives of the several international managers (collectively, the
"Underwriters"), and the IPO shall have closed and settled.

          Section 4.2  Conditions to the Company's Obligations. The obligation
                       ---------------------------------------
of the Company to sell and accept payment for, and deliver, the Reserved Shares
to each of the Purchasers at the Closing shall be subject to the satisfaction of
the following conditions as of the Closing Date:

          (i)    Each of the Purchasers shall have delivered the executed Lock-
Up Agreements and the Power of Attorney to the Company on or prior to the date
of the execution of this Agreement;

          (ii)   the Commission shall have declared the Registration Statement
effective; and

          (iii)  the Underwriters shall have purchased the Shares from the
Company and IPO shall have closed and settled.

                                   ARTICLE V
                                   EXPENSES

          Each party shall pay its own expenses incurred in connection with the
transactions contemplated hereby, except that the Company shall pay all fees and
expenses incurred to register the Reserved Shares with the Commission and issue
the Reserved Shares.

                                   ARTICLE VI
                                   TERMINATION

          This Agreement shall become effective upon the execution and delivery
of this Agreement by the parties hereto.  This Agreement may be terminated at
any time on or prior to the Closing Date by either the Company or any of the
Purchasers by written notice to the other if the Underwriting Agreement is
terminated.

                                       7
<PAGE>

                                  ARTICLE VII
                                 MISCELLANEOUS

          Section 7.1  Governing Law.  This Agreement shall be governed in all
                       -------------
respects by the laws of the State of Delaware.

          Section 7.2  Survival.  The representations, warranties, covenants and
                       --------
agreements made herein shall survive any investigation made by the Purchasers
and the closing of the transactions contemplated hereby.  All statements as to
factual matters contained in any certificate or other instrument delivered by or
on behalf of the Company pursuant hereto in connection with the transactions
contemplated hereby shall be deemed to be representations and warranties by the
Company hereunder solely as of the date of such certificate or instrument.

          Section 7.3  Successors and Assigns.  Except as otherwise expressly
                       ----------------------
provided herein, the provisions hereof shall inure to the benefit of, and be
binding upon, the successors, assigns, heirs, executors and administrators of
the parties hereto and shall inure to the benefit of and be enforceable by each
person who shall be a holder of the Shares from time to time.

          Section 7.4  Entire Agreement.  This Agreement, the Power of Attorney,
                       ----------------
the Schedules and the other documents delivered pursuant hereto constitute the
full and entire understanding and agreement between the parties with regard to
the subjects hereof and no party shall be liable or bound to any other in any
manner by any representations, warranties, covenants and agreements except as
specifically set forth herein and therein.

          Section 7.5  Separability.  In case any provision of the Agreement
                       ------------
shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

          Section 7.6  Amendment and Waiver.  This Agreement may be amended or
                       --------------------
modified only upon the mutual written consent of the Company and the Purchasers.

          Section 7.7  Notices.  All notices required or permitted hereunder
                       -------
shall be in writing and shall be deemed effectively given: (i) upon personal
delivery to the party to be notified; (ii) when sent by confirmed telex or
facsimile if sent during normal business hours of the recipient, if not, then on
the next business day; (iii) five (5) days after having been sent by registered
or certified mail, return receipt requested, postage prepaid; or (iv) one (1)
day after deposit with a nationally recognized overnight courier, special next
day delivery, with verification of receipt.  All communications shall be sent to
the Company at 112100 Sunset Hills Road, Suite 110, Reston, Virginia 20190,
Attention: Matt S. Nydell, General Counsel, and to a Purchaser at the address
set forth on Schedule I attached hereto or at such other address as the Company
             ----------
or Purchaser may designate by ten (10) days advance written notice to the other
parties hereto.

          Section 7.8  Counterparts.  This Agreement may be executed in any
                       ------------
number of counterparts, each of which shall be an original, but all of which
together shall

                                       8
<PAGE>

constitute one instrument.

          Section 7.9  Broker's Fees.  Each party hereto represents and warrants
                       -------------
that no agent, broker, investment banker, person or firm acting on behalf of or
under the authority of such party hereto is or will be entitled to any broker's
or finder's fee or any other commission directly or indirectly in connection
with the transactions contemplated herein.  Each party hereto further agrees to
indemnify each other party for any claims, losses or expenses incurred by such
other party as a result of its representation in this Article VII, Section 9
being untrue.

                   [SIGNATURES APPEAR ON THE FOLLOWING PAGE]

                                       9
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have executed the Agreement as
of the date set forth in the first paragraph hereof.

                         COMPANY:

                         VIA NET.WORKS, Inc., a Delaware Corporation

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         PURCHASERS:

                         CENTENNIAL FUND V, L.P.

                         By: Centennial Holdings V, L.P., its General Partner

                             By:_________________________________
                             Name:_______________________________
                             Title:______________________________

                         CENTENNIAL HOLDINGS I, LLC

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         CENTENNIAL ENTREPRENEURS FUND V, L.P.

                         By: Centennial Holdings V, L.P., its General Partner

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         CENTENNIAL FUND VI, L.P.

                         By: Centennial Holdings VI, L.P., its General Partner

                             By:_________________________________
                             Name:_______________________________
                             Title:______________________________

                                       10
<PAGE>

                         MILLENNIAL HOLDINGS LLC

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         NORWEST EQUITY CAPITAL, L.L.C.

                         By: Itasca NEC, L.L.C., its Managing Member

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BESSEMER VENTURE INVESTORS L.P.

                         By: Deer IV & Co. LLC

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BESSEMER VENTURE PARTNERS IV L.P.

                         By: Deer IV & Co. LLC

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BESSEC VENTURES IV L.P.

                         By: Deer IV & Co. LLC

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                                       11
<PAGE>

                         BOSTON MILLENNIA PARTNERS LIMITED PARTNERSHIP

                         By: Glen Partners Limited Partnership, its General
                             Partner

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BOSTON MILLENNIA ASSOCIATES I PARTNERSHIP

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         RHO MANAGEMENT TRUST I

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         CITIZENS CAPITAL, INC.

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         CHESTNUT INVESTMENT ASSOCIATES 1998

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         PROVIDENCE EQUITY PARTNERS L.P.

                         By: Providence Equity Partners LLC, its General Partner

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                                       12
<PAGE>

                         PROVIDENCE EQUITY PARTNERS II L.P.

                         By: Providence Equity Partners LLC, its General Partner

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BCI GROWTH V, L.P.

                         By: ______________________, its General Partner

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                         BCI INVESTORS, L.L.C.

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         SIS INTERNATIONAL HOLDING, INC.

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         FIMA FINANCE MANAGEMENT, INC.

                         By:_____________________________________
                         Name:___________________________________
                         Title:__________________________________

                         FIRST UNION MERCHANT BANKING, LLC-1999

                         By: FUCP Management Company, LLC-1999, its Managing
                             Member

                            By:__________________________________
                            Name:________________________________
                            Title:_______________________________

                                       13
<PAGE>

                         _________________________________________
                         JOSEF VON RICKENBACH

                         _________________________________________
                         JOSHUA B. TANZER

                         _________________________________________
                         ALLYN C. WOODWARD, JR.

                         _________________________________________
                         JOHN G. PUENTE

                         _________________________________________
                         LEON SAYNAVE

                                       14
<PAGE>

                                   SCHEDULE I
                                   ----------

                             SCHEDULE OF PURCHASERS

<TABLE>
<CAPTION>

                                                Number                  Purchase
                  Name and Address              of Shares                 Price
                  ----------------              ---------               --------
<S>                                             <C>                      <C>
Centennial Fund V, L.P.
1428 Fifteenth Street
Denver, CO  80202

Centennial Entrepreneurs Fund V, L.P.
1428 Fifteenth Street
Denver, CO  80202

Centennial Holdings I, LLC
1428 Fifteenth Street
Denver, CO  80202

Centennial Fund VI, L.P.
1428 Fifteenth Street
Denver, CO  80202

Norwest Equity Capital, L.L.C.
2800 Piper Jaffrey Tower
222 South Ninth Street
Minneapolis, MN 55402

Millennial Holdings LLC
1428 Fifteenth Street
Denver, CO 80202

Bessemer Venture Investors L.P.
Bessemer Venture Partners IV L.P.
Bessec Ventures IV L.P.
83 Walnut Street
Wellesley Hills, MA 02481

IAI World Fund, LLC
800 La Salle Avenue
Suite 2250
Minneapolis, MN 55402

Eagle Ventures WF, LLC
800 La Salle Avenue
Suite 2250
Minneapolis, MN 55402
</TABLE>

                                       15
<PAGE>

<TABLE>
<CAPTION>

                                                Number                  Purchase
                  Name and Address              of Shares                 Price
                  ----------------              ---------               --------
<S>                                             <C>                      <C>
Providence Equity Partners, L.P.
50 Kennedy Plaza 9th Floor
Providence, RI 02903

Providence Equity Partners II L.P.
50 Kennedy Plaza 9th Floor
Providence, RI 02903

BCI Growth V, L.P.
Glenpointe Centre West
Teaneck, NJ 07666

BCI Investors, L.L.C.
Glenpointe Centre West
Teaneck, NJ 07666

SIS International Holding, Inc.
12450 Fair Lakes Circle, Suite 370
Fairfax, VA 22033

FIMA Finance Management, Inc.
c/o Sadco S.A
Voltastrasse 61
P.O. Box 3328044
Zurich, Switzerland

First Union Merchant Banking, LLC-1999
One First Union Center
302 S. College Street
5th Floor
Charlotte, NC 28288-0732

Boston Millennia Partners Limited Partnership
30 Rowes Wharf, Suite 330
Boston, MA  02110
Attn:  Marty Hernon

Boston Millennia Associates I Partnership
30 Rowes Wharf, Suite 300
Boston, MA  02110
Attn:  Marty Hernon

Josef von Rickenbach
31 Fairbanks Road
Lexington, MA  02173

Chestnut Investment Associates 1998
One Financial Center, 28th Floor
</TABLE>

                                       16
<PAGE>

<TABLE>
<CAPTION>

                                                Number                  Purchase
                  Name and Address              of Shares                 Price
                  ----------------              ---------               --------
<S>                                             <C>                      <C>
Boston, MA  02111
Attn:  Albert A. Holman, III

Allyn C. Woodward, Jr.
14 Meadowbrook Road
Wellesley, MA  02181-1107

Rho Management Trust I
150 West 57th Street
New York, NY  10019
Attn:  Daniele Boder

Joshua B. Tanzer
2400 Hanover Street
Palo Alto, CA 94304

Citizens Capital, Inc.
28 State Street, 15th Floor
Boston, MA  02109
Attn:  Robert E. Garrow

John G. Puente
10500 Willowbrook Drive
Potomac, MD 20854

Leon Saynave
1 Bosweg
1860 Meise
Belgium
</TABLE>

                                       17
<PAGE>

                                   EXHIBIT A
                                   ---------

                           FORM OF POWER OF ATTORNEY
<PAGE>

                                                                Exhibit A

                              VIA NET.WORKS, Inc.

                               Power of Attorney
                               -----------------

                               February __, 2000

Matt S. Nydell
Vice President, General Counsel and Secretary
VIA NET.WORKS, Inc.
12100 Sunset Hills Road
Suite 110
Reston, Virginia

          The undersigned (the "Purchaser") proposes to enter into a Purchase
Agreement (the "Purchase Agreement") with VIA NET.WORKS, Inc., a Delaware
corporation (the "Company"), pursuant to which the Company has proposed to sell
to the Purchaser, and the Purchaser has proposed to buy from the Company, the
number of shares of common stock, par value $0.001 per share, set forth opposite
such Purchaser's name in Schedule I attached to the Purchase Agreement (the
                         ----------
"Reserved Shares") at a price per share offered to the public.

          The Purchaser acknowledges that the Company has provided the Purchaser
with (i) a preliminary copy of the Purchase Agreement and (ii) a copy of the
prospectus which comprises a part of the Registration Statement.  Capitalized
terms not otherwise defined herein shall have the meanings set forth in the
Purchase Agreement.

          The Purchaser hereby executes and delivers this power of attorney
(this "Power of Attorney") to the persons named in the following paragraph,
intending to be legally bound, for the following uses and purposes:

          The Purchaser hereby irrevocably constitutes and appoints Ms.
Catherine A. Graham and Mr. Matt S. Nydell, and either of them acting singly,
with full power of substitution, the true and lawful attorneys-in-fact (the
"Attorneys") of the Purchaser, with full power in the name of, for and on behalf
of, the Purchaser with respect to all matters arising in connection with the
execution of the Purchase Agreement including, but not limited to, the power and
authority to take any and all of the following actions:

          (1) To purchase from the Company pursuant to the Purchase Agreement
such number of the Reserved Shares set forth opposite the Purchaser's name in
Schedule I to the Purchase Agreement;
----------
<PAGE>

          (2) For the purpose of effecting such purchase, to execute and deliver
the Purchase Agreement at the public offering price per Share to be determined
by the Company together with the Underwriters, which public offering price shall
be the purchase price per Reserved Share (the "Purchase Price"), provided that
the Purchase Price per Reserved Share shall not be greater than [$_____];

          (3) On behalf of the Purchaser, to make the representations and
warranties;

          (4) To incur any necessary or appropriate expense in connection with
the purchase of the Reserved Shares;

          (5) To make, execute, acknowledge and deliver all such other
contracts, orders, receipts, notices, instructions, certificates, letters and
other writings, and in general to do all things and to take all actions which
the Attorneys, in their sole discretion, may consider necessary or proper in
connection with or to carry out the aforesaid purchase of the Reserved Shares
from the Company and the execution and delivery of the Purchase Agreement, as
fully as could the Purchaser if personally present and acting; and

          (6) To sign such other documents and agreements as necessary to
consummate this transaction.

          The Attorneys are hereby empowered to determine in their sole
discretion the time or times when, purpose for and manner in which any power
herein conferred upon them shall be exercised, and the conditions, provisions or
covenants of any instrument or document which may be executed by them pursuant
hereto.  Each of the Attorneys appointed by the Purchaser herein shall have full
power and authority to make and constitute in his or her place and stead a
substituted attorney-in-fact, and the Purchaser hereby ratifies and confirms all
that the aforesaid attorneys-in-fact or substitute or substitutes shall do
pursuant to paragraphs 1 through 6 above.  All actions hereunder may be taken by
either one of said Attorneys or their respective substitutes.

          This Power of Attorney is an agency coupled with an interest and all
authority conferred hereby shall be irrevocable, and shall not be terminated by
                           --------------------
any act of the Purchaser or by operation of law, whether by the dissolution or
liquidation of any corporation or partnership if the Purchaser is a corporation
or partnership, or death or incapacity of the Purchaser if the Purchaser is a
natural

                                       2
<PAGE>

person, or by the occurrence of any other event or events, including,
without limiting the foregoing, the termination of any trust or estate for which
the Purchaser is acting as a fiduciary or fiduciaries).

          This Power of Attorney shall automatically terminate as soon as the
Reserved Shares being purchased by the Purchaser from the Company have been
delivered and paid for as provided in the Purchase Agreement.  Notwithstanding
any of the foregoing provisions, if all of the transactions contemplated by the
Purchase Agreement and this Power of Attorney are not completed prior to
February 29, 2000, then from and after such date, the Purchaser shall have the
power, upon written notice to the Attorneys, to terminate this Power of Attorney
subject, however, to all lawful action done or performed pursuant hereto prior
to the receipt of actual notice.

          All representations and warranties of the Purchaser in Section 3.3 of
Article III of the Purchase Agreement are, with respect to the Purchaser, and
will be at the Closing Date as determined in accordance with the Purchase
Agreement, true and correct and will, as provided in the Purchase Agreement,
survive the termination of the Purchase Agreement and the delivery of and
payment for the Reserved Shares.  In addition, the Purchaser has complied or
will comply with all agreements required for the consummation of the
transactions contemplated by the Purchase Agreement applicable to the Purchaser
and has satisfied or will satisfy all conditions therein applicable to the
Purchaser to be performed or satisfied by such date.

          Upon the execution and delivery of the Purchase Agreement by the
Attorneys on behalf of the Purchaser, the Purchaser agrees to be bound by and to
perform each and every covenant and agreement therein of the Purchaser.

          The Purchaser will immediately notify the Attorneys of the occurrence
of any event which causes the representations, warranties and agreements
contained herein or in the Purchase Agreement not to be true and correct and in
full force and effect at the effective date of the Registration Statement and at
the Closing Date.

          The Attorneys, and any of them, shall be entitled to act and rely upon
any representation, warranty, agreement, statement, request, notice or
instructions respecting this Power of Attorney given by the Purchaser, not only
as to the authorization, validity and effectiveness thereof, but also as to the
truth and acceptability of any information therein contained; provided, however,
that any statement or notice to the Attorneys with respect to the date of
delivery under the Purchase Agreement or with respect to the non-effectiveness
or termination of the Purchase Agreement, or advice that the Purchase Agreement
has not been executed and delivered, shall have been confirmed in writing to the
Attorneys by the

                                       3
<PAGE>

Company.  In acting hereunder, the Attorneys may also rely on
the representations, warranties and agreements of the Purchaser made in the
Purchase Agreement executed by the Attorneys on behalf of the Purchaser.

          It is understood that the Attorneys assume no responsibility or
liability to any person other than to execute and deliver the Purchase Agreement
on behalf of the Purchaser.  The Attorneys (in such a capacity) make no
representations with respect to, and shall have no responsibility for, the
Registration Statement nor, except as herein expressly provided, for any aspect
of the offering of Reserved Shares, and the Attorneys shall not be liable for
any error of judgment or for any act done or omitted or for any mistake of fact
or law except for the Attorneys' own gross negligence or bad faith.  The
Purchaser agrees to indemnify the Attorneys for and to hold the Attorneys,
jointly and severally, free from and harmless against any and all loss, claim,
damage, liability or expense incurred by or on behalf of the Attorneys, or any
of them, arising out of or in connection with acting as Attorneys under this
Power of Attorney, as well as the cost and expense of defending against any
claim of liability hereunder, and not due to the Attorneys' own gross negligence
or bad faith.  The Purchaser agrees that the Attorneys may consult with counsel
of their choice (which may but need not be counsel for the Company) and the
Attorneys shall have full and complete authorization and protection for any
action taken or suffered by the Attorneys, or any of them hereunder, in good
faith and in accordance with the opinion of such counsel.  The Attorneys shall
serve entirely without compensation.

          If any provision of this Power of Attorney is found to be
unenforceable as applied in any particular case or circumstances in any
applicable jurisdiction because it conflicts with any other provision of this
Power of Attorney, or any constitution, statute or rule of public policy, or for
any other reason, such finding will not render the provision unenforceable in
any other case or circumstances, or render any other provision of this Power of
Attorney unenforceable to any extent whatsoever.

          This Power of Attorney shall be binding upon the Purchaser and its
personal representatives, successors and assigns, as the case may be.

          This Power of Attorney shall be governed by the laws of the
Commonwealth of Virginia, without giving effect to the choice of law provisions
thereof.

          This Power of Attorney may be executed in one or more counterparts,
each of which shall be deemed to be an original, but all of which shall be one
and the same document.

                                       4
<PAGE>

          Witness the due execution of the foregoing Power of Attorney as of the
date written below.

Dated:  February ___, 2000                      Very truly yours,

                                                NAME OF PURCHASER

                                                ________________________________

                                                By:_____________________________
                                                Name:___________________________
                                                Title:__________________________

                                                Address:

                                                ________________________________

                                                ________________________________

                                                ________________________________

                                                ________________________________

Instruction:  The signature(s) above must be notarized.  Please have a licensed
-----------                                  ---------
Notary Public execute the notarial acknowledgment on the last page of this Power
of Attorney.

                                       5
<PAGE>

                            NOTARIAL ACKNOWLEDGMENT

State or Commonwealth of ________________

County/City of ________________

       On this the ___ day of ___________, 2000, before the undersigned Notary
Public, personally appeared ___________________________________, proved to me on
the basis of satisfactory evidence to be the person(s) who executed this
instrument, and acknowledged that they subscribed their names to this instrument
on their own behalf.

                                        WITNESS my hand and official seal.

                                        ____________________________________
                                        Notary's Signature

My commission expires:

_______________________

                                       6

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