[CentOS] CentOS Stream 8 dnf fails

Every time I run dnf, I get this:

========= [root@vmhost2 ~]# dnf upgrade CentOS Linux 8 - AppStream 70 B/s | 38 B 00:00 Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist =========

I tried disabling the repository, but that only gives me exactly the same error for the baseos repository. I doubt it is a problem in the .repo files. Something else is going on.

Ping to mirrorlist.centos.org works on both ipv4 and ipv6, so I know that both name resolution and network connectivity are working.

Thanks!

======== Bill Gee