EXHIBIT 23.1 [ERNST & YOUNG LOGO] CONSENT OF INDEPENDENT AUDITORS We consent to the reference to our firm under the caption "Experts", and to the use of our report dated March 2, 2000 in the Registration Statement (Form S-1) and related Prospectus of XACCT Technologies Ltd. for the registration of its ordinary shares. Tel-Aviv, Israel July 26, 2000 /s/ Kost, Forer & Gabbay KOST FORER & GABBAY A member of Ernst & Young international Kost, Forer & Gabbay is a member of Ernst & Young International, Ltd.