$ sudo apt update

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

Hit:1 http://security.ubuntu.com/ubuntu bionic-security InRelease
Err:2 http://au.archive.ubuntu.com/ubuntu bionic InRelease
  Could not connect to au.archive.ubuntu.com:80 (2001:388:30bc:cafe::beef). - connect (111: Connection refused) Could not connect to au.archive.ubuntu.com:80 (202.158.214.106). - connect (111: Connection refused)
Err:3 http://au.archive.ubuntu.com/ubuntu bionic-updates InRelease
  Unable to connect to au.archive.ubuntu.com:http:
Err:4 http://au.archive.ubuntu.com/ubuntu bionic-backports InRelease
  Unable to connect to au.archive.ubuntu.com:http:
Reading package lists...
Building dependency tree...
Reading state information...
3 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Could not connect to au.archive.ubuntu.com:80 (2001:388:30bc:cafe::beef). - connect (111: Connection refused) Could not connect to au.archive.ubuntu.com:80 (202.158.214.106). - connect (111: Connection refused)
W: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Unable to connect to au.archive.ubuntu.com:http:
W: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Unable to connect to au.archive.ubuntu.com:http:
W: Some index files failed to download. They have been ignored, or old ones used instead.