EXHIBIT 5.1 August 4, 1999 IFX Corporation 707 Skokie Boulevard 5th Floor Northbrook, Illinois, 60062 Re: Registration Statement on Form S-3 Gentlemen: We have acted as counsel to IFX Corporation, a Delaware corporation (the "Company"), in connection with the preparation and filing with the Securities and Exchange Commission under the Securities Act of 1933, as amended, of the Company's Registration Statement on Form S-3 (the "Registration Statement") relating to the proposed offering of 16,758 shares of Common Stock, $.02 par value per share (the "Common Stock"), of the Company by a certain selling stockholder. As to certain factual matters material to this opinion, we have relied, without independent investigation, upon (i) statements, certificates, representations and warranties of the Company and its directors, officers and duly appointed agents, and (ii) such certificates or statements of public officials as we have deemed relevant or necessary. In such examinations, we have assumed the genuineness of all signatures and the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as conformed or photostatic copies. Based upon the foregoing, we are of the opinion that the shares of Common Stock which are the subject of the Registration Statement have been duly and validly issued and are fully paid and non-assessable. We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the reference to our firm under the heading "Legal Matters" in the Prospectus comprising a part of the Registration Statement. Very truly yours, /s/ NEAL, GERBER & EISENBERG