<PAGE>
EXHIBIT 23.1
CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
We consent to the reference to our firm in the Registration Statement on Form
S-8 pertaining to the 1997 Stock Plan; 1997 Employee Stock Purchase Plan; The
Concentric Networks United Kingdom Limited Share Option Scheme; and, The
Concentric Network Corporation Netherlands Share Option Scheme and to the
incorporation by reference therein of our report dated January 21, 2000 (except
for Note 13, as to which the date is March 20, 2000), with respect to the
consolidated financial statements and schedule of Concentric Network Corporation
included in its Annual Report (Form 10-K and Form 10-K/A) for the year ended
December 31, 1999, filed with the Securities and Exchange Commission.
/s/ Ernst & Young LLP
San Jose, California
June 9, 2000
