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

http://alt.centos5.zswap.net/7.8.2003/isos/aarch64/
http://mirror.vcu.edu/pub/gnu_linux/centos-altarch/7.8.2003/isos/aarch64/

http://mirror.pit.teraswitch.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirrors.xtom.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.keystealth.org/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.dal.nexril.net/centos-altarch/7.8.2003/isos/aarch64/
http://alt.centos3.zswap.net/7.8.2003/isos/aarch64/
http://mirror.atl.genesisadaptive.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirrors.ocf.berkeley.edu/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.facebook.net/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.chpc.utah.edu/pub/centos-altarch/7.8.2003/isos/aarch64/
http://ftp.osuosl.org/pub/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.genesisadaptive.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.lax.genesisadaptive.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.genesishosting.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.math.princeton.edu/pub/centos-altarch/7.8.2003/isos/aarch64/
http://repos.eggycrew.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.esecuredata.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.calgah.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.cedia.org.ec/centos-altarch/7.8.2003/isos/aarch64/
http://mirrors.tuna.tsinghua.edu.cn/centos-altarch/7.8.2003/isos/aarch64/
http://ftp.bme.hu/centos-altarch/7.8.2003/isos/aarch64/
http://centosaltarch.quelquesmots.fr/7.8.2003/isos/aarch64/
http://mirror.serverion.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.infonline.de/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.init7.net/centos-altarch/7.8.2003/isos/aarch64/
http://mirror.ehv.weppel.nl/centos-altarch/7.8.2003/isos/aarch64/
http://ftp.agdsn.de/pub/mirrors/centos-altarch/7.8.2003/isos/aarch64/
http://mirrors.daticum.com/centos-altarch/7.8.2003/isos/aarch64/
http://mirrors.xtom.nl/centos-altarch/7.8.2003/isos/aarch64/
+ others, see the full list of mirrors: https://www.centos.org/download/altarch-mirrors/

Mirrors verified Thu Sep 24 21:20:55 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