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                                                                    Exhibit 23.3

               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS


We consent to the reference to our firm under the caption "Experts" in
Amendment No. 1 to the Registration Statement (Form S-3 No. 333-54790) and
related prospectus of XO Communications, Inc., and to the incorporation by
reference therein of our reports dated January 21, 2000, exceptfor note 13, as
to which the date is March 20, 2000, with respect to the consolidated financial
statements and schedule of Concentric Network Corporation for the year ended
December 31, 1999, included in XO Communications, Inc.'s (formerly NEXTLINK
Communications Inc.) Form 8-K/A dated August 21, 2000, filed with the
Securities and Exchange Commission.


/s/ Ernst & Young LLP

San Jose, California
March 12, 2001