In order to conserve the limited bandwidth available, ISO images are not downloadable from mirror.centos.org

http://repos-va.psychz.net/centos/7.7.1908/isos/x86_64/
http://mirror.ash.fastserv.com/centos/7.7.1908/isos/x86_64/
http://mirror.centos.iad1.serverforge.org/7.7.1908/isos/x86_64/
http://centos4.zswap.net/7.7.1908/isos/x86_64/
http://mirror.vcu.edu/pub/gnu_linux/centos/7.7.1908/isos/x86_64/
http://mirrors.advancedhosters.com/centos/7.7.1908/isos/x86_64/
http://mirror.cs.vt.edu/pub/CentOS/7.7.1908/isos/x86_64/
http://mirror.cogentco.com/pub/linux/centos/7.7.1908/isos/x86_64/
http://mirror.vtti.vt.edu/centos/7.7.1908/isos/x86_64/
http://us.mirror.nsec.pt/centos/7.7.1908/isos/x86_64/
http://repo1.ash.innoscale.net/centos/7.7.1908/isos/x86_64/

http://mirror.nodesdirect.com/centos/7.7.1908/isos/x86_64/
http://mirror.pit.teraswitch.com/centos/7.7.1908/isos/x86_64/
http://mirror.wdc1.us.leaseweb.net/centos/7.7.1908/isos/x86_64/
http://centos-distro.cavecreek.net/centos/7.7.1908/isos/x86_64/
http://centos.sonn.com/7.7.1908/isos/x86_64/
http://repo.miserver.it.umich.edu/centos/7.7.1908/isos/x86_64/
http://mirrors.lug.mtu.edu/centos/7.7.1908/isos/x86_64/
http://mirror.mia11.us.leaseweb.net/centos/7.7.1908/isos/x86_64/
http://mirror.cisp.com/CentOS/7.7.1908/isos/x86_64/
http://repos-tx.psychz.net/centos/7.7.1908/isos/x86_64/
http://mirrors.syringanetworks.net/centos/7.7.1908/isos/x86_64/
http://mirror.lug.udel.edu/pub/centos/7.7.1908/isos/x86_64/
http://linux.mirrors.es.net/centos/7.7.1908/isos/x86_64/
http://mirror.linux.duke.edu/pub/centos/7.7.1908/isos/x86_64/
http://mirror.centos.lax1.serverforge.org/7.7.1908/isos/x86_64/
http://mirrors.mit.edu/centos/7.7.1908/isos/x86_64/
http://ewr.edge.kernel.org/centos/7.7.1908/isos/x86_64/
http://repos.mia.quadranet.com/centos/7.7.1908/isos/x86_64/
http://centos.den.host-engine.com/7.7.1908/isos/x86_64/
+ others, see the full list of mirrors: https://www.centos.org/download/mirrors/

Mirrors verified Tue Mar 31 10:24:40 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