In order to conserve the limited bandwidth available, ISO images are not downloadable from mirror.centos.org
The following mirrors should have the ISO images available:
http://ftp.osuosl.org/pub/centos/8.1.1911/isos/x86_64/
http://mirror.steadfastnet.com/centos/8.1.1911/isos/x86_64/
http://mirror.linux.duke.edu/pub/centos/8.1.1911/isos/x86_64/
http://mirror.atlanticmetro.net/centos/8.1.1911/isos/x86_64/
http://mirrors.umflint.edu/CentOS/8.1.1911/isos/x86_64/
http://centos.s.uw.edu/centos/8.1.1911/isos/x86_64/
http://mirror.cs.pitt.edu/centos/8.1.1911/isos/x86_64/
http://repos-tx.psychz.net/centos/8.1.1911/isos/x86_64/
http://centos.host-engine.com/8.1.1911/isos/x86_64/
http://mirror.centos.lax1.serverforge.org/8.1.1911/isos/x86_64/
http://mirror.ilumno.com/centos/8.1.1911/isos/x86_64/
http://mirror.mobap.edu/centos/8.1.1911/isos/x86_64/
http://mirrors.maine.edu/CentOS/8.1.1911/isos/x86_64/
http://mirror.genesishosting.com/centos/8.1.1911/isos/x86_64/
http://mirror.mia11.us.leaseweb.net/centos/8.1.1911/isos/x86_64/
http://repo.ialab.dsu.edu/centos/8.1.1911/isos/x86_64/
http://centos-distro.cavecreek.net/centos/8.1.1911/isos/x86_64/
http://repos.dfw.quadranet.com/centos/8.1.1911/isos/x86_64/
http://mirror.sesp.northwestern.edu/centos/8.1.1911/isos/x86_64/
http://mirrors.codec-cluster.org/centos/8.1.1911/isos/x86_64/
http://centos4.zswap.net/8.1.1911/isos/x86_64/
http://mirror.cc.columbia.edu/pub/linux/centos/8.1.1911/isos/x86_64/
http://mirror.vcu.edu/pub/gnu_linux/centos/8.1.1911/isos/x86_64/
http://repo1.sea.innoscale.net/centos/8.1.1911/isos/x86_64/
http://mirrors.greenmountainaccess.net/centos/8.1.1911/isos/x86_64/
http://mirrors.xmission.com/centos/8.1.1911/isos/x86_64/
http://sjc.edge.kernel.org/centos/8.1.1911/isos/x86_64/
http://mirrors.tripadvisor.com/centos/8.1.1911/isos/x86_64/
http://mirrors.ocf.berkeley.edu/centos/8.1.1911/isos/x86_64/
http://mirror.clarkson.edu/centos/8.1.1911/isos/x86_64/
+ others, see the full list of mirrors: https://www.centos.org/download/mirrors/
Mirrors verified Mon Jun 15 05:34:43 2020 UTC
You can also download the ISO images using bittorrent, a peer-to-peer file sharing protocol. The .torrent files can be found from CentOS mirrors. Various bittorrent clients are available, including (in no particular order of preference): utorrent, vuze (Azureus), BitTorrent, Deluge, ctorrent, ktorrent, rtorrent and transmission. Packaged copies of various torrent clients for CentOS can be found in the repositories listed in the following wiki article: https://wiki.centos.org/AdditionalResources/Repositories
The following mirrors should have the ISO images available:
http://ftp.osuosl.org/pub/centos/8.1.1911/isos/x86_64/
http://mirror.steadfastnet.com/centos/8.1.1911/isos/x86_64/
http://mirror.linux.duke.edu/pub/centos/8.1.1911/isos/x86_64/
http://mirror.atlanticmetro.net/centos/8.1.1911/isos/x86_64/
http://mirrors.umflint.edu/CentOS/8.1.1911/isos/x86_64/
http://centos.s.uw.edu/centos/8.1.1911/isos/x86_64/
http://mirror.cs.pitt.edu/centos/8.1.1911/isos/x86_64/
http://repos-tx.psychz.net/centos/8.1.1911/isos/x86_64/
http://centos.host-engine.com/8.1.1911/isos/x86_64/
http://mirror.centos.lax1.serverforge.org/8.1.1911/isos/x86_64/
http://mirror.ilumno.com/centos/8.1.1911/isos/x86_64/
http://mirror.mobap.edu/centos/8.1.1911/isos/x86_64/
http://mirrors.maine.edu/CentOS/8.1.1911/isos/x86_64/
http://mirror.genesishosting.com/centos/8.1.1911/isos/x86_64/
http://mirror.mia11.us.leaseweb.net/centos/8.1.1911/isos/x86_64/
http://repo.ialab.dsu.edu/centos/8.1.1911/isos/x86_64/
http://centos-distro.cavecreek.net/centos/8.1.1911/isos/x86_64/
http://repos.dfw.quadranet.com/centos/8.1.1911/isos/x86_64/
http://mirror.sesp.northwestern.edu/centos/8.1.1911/isos/x86_64/
http://mirrors.codec-cluster.org/centos/8.1.1911/isos/x86_64/
http://centos4.zswap.net/8.1.1911/isos/x86_64/
http://mirror.cc.columbia.edu/pub/linux/centos/8.1.1911/isos/x86_64/
http://mirror.vcu.edu/pub/gnu_linux/centos/8.1.1911/isos/x86_64/
http://repo1.sea.innoscale.net/centos/8.1.1911/isos/x86_64/
http://mirrors.greenmountainaccess.net/centos/8.1.1911/isos/x86_64/
http://mirrors.xmission.com/centos/8.1.1911/isos/x86_64/
http://sjc.edge.kernel.org/centos/8.1.1911/isos/x86_64/
http://mirrors.tripadvisor.com/centos/8.1.1911/isos/x86_64/
http://mirrors.ocf.berkeley.edu/centos/8.1.1911/isos/x86_64/
http://mirror.clarkson.edu/centos/8.1.1911/isos/x86_64/
+ others, see the full list of mirrors: https://www.centos.org/download/mirrors/
Mirrors verified Mon Jun 15 05:34:43 2020 UTC
You can also download the ISO images using bittorrent, a peer-to-peer file sharing protocol. The .torrent files can be found from CentOS mirrors. Various bittorrent clients are available, including (in no particular order of preference): utorrent, vuze (Azureus), BitTorrent, Deluge, ctorrent, ktorrent, rtorrent and transmission. Packaged copies of various torrent clients for CentOS can be found in the repositories listed in the following wiki article: https://wiki.centos.org/AdditionalResources/Repositories