aptはdebian 11 Bullseyeをアップデートするときに「deb.debian.org」を確認できません。

Debian 11 Bullseyeをインストールしましたが、これは私のsource.listファイルです：

deb http://deb.debian.org/debian bullseye main contrib non-free
deb-src http://deb.debian.org/debian bullseye main contrib non-free

deb http://security.debian.org/debian-security bullseye-security main contrib non-free
deb-src http://security.debian.org/debian-security bullseye-security main contrib non-free

deb http://deb.debian.org/debian bullseye-updates main contrib non-free
deb-src http://deb.debian.org/debian bullseye-updates main contrib non-free

deb http://deb.debian.org/debian bullseye-backports main contrib non-free
deb-src http://deb.debian.org/debian bullseye-backports main contrib non-free

更新を使用しようとすると、apt update次のエラーが発生します。

Err:1 http://deb.debian.org/debian bullseye InRelease
Could not resolve 'deb.debian.org'
Err:2 http://security.debian.org.debian-security bullseye InRelease
Could not resolve 'deb.debian.org'
Err:3 http://deb.debian.org/debian bullseye-updates InRelease
Could not resolve 'deb.debian.org'
Err:4 http://security.debian.org.debian bullseye-backports InRelease
Could not resolve 'deb.debian.org'
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://deb.debian.org/debian/dists/bullseye/InRelease Could not resolve 'deb.debian.org'
W: Failed to fetch http://security.debian.org/debian-security/dists/bullseye-security/InRelease Could not resolve 'security.debian.org'
W: Failed to fetch http://deb.debian.org/debian/dists/bullseye-updates/InRelease Could not resolve 'deb.debian.org'
W: Failed to fetch http://deb.debian.org/debian/dists/bullseye-backports/InRelease Could not resolve 'deb.debian.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.

私のsource.listファイルに何の問題がありますか？また設定がありますか？