I've checked in our mirrors DB and I don't see any reference to ibiblio
so it seems that mirror has never been publicly announced or inserted in
the DB.
Can you get your mirror updated and then tell us when done ? (see
http://wiki.centos.org/HowTos/CreatePublicMirrors)
I'll then add it .

HTTP: http://distro.ibiblio.org/centos/
FTP: ftp://distro.ibiblio.org/centos/
RSYNC: coming soon

Sync schedule: Every 4 hrs
Bandwidth: 1GB/s
Location: Chapel Hill, North Carolina
Sponsor: ibiblio.org
Sponsor URL: http://www.ibiblio.org
IP to authorize: 152.19.134.30
Email contact: dls@ibiblio.org