Не, прокси не кэширующий, его задача просто быть отверстием в мир)
Ну и чтоб исключить его влияние, т.к. на нем такой же альт и такое же поведение вот аналогичный прямой сценарий без проксей (с самого прокси-сервера)
# apt-get update
Get:1 ftp://ftp.altlinux.org c8/branch/x86_64 release [884B]
Get:2 ftp://ftp.altlinux.org c8/branch/x86_64-i586 release [543B]
Get:3 ftp://ftp.altlinux.org c8/branch/noarch release [679B]
Fetched 2106B in 0s (23.2kB/s)
Hit ftp://ftp.altlinux.org c8/branch/x86_64/classic pkglist
Hit ftp://ftp.altlinux.org c8/branch/x86_64/classic release
Hit ftp://ftp.altlinux.org c8/branch/x86_64-i586/classic pkglist
Hit ftp://ftp.altlinux.org c8/branch/x86_64-i586/classic release
Hit ftp://ftp.altlinux.org c8/branch/noarch/classic pkglist
Hit ftp://ftp.altlinux.org c8/branch/noarch/classic release
Reading Package Lists... Done
Building Dependency Tree... Done
# nslookup ftp.altlinux.org
Server: 127.0.0.1
Address: 127.0.0.1#53
Non-authoritative answer:
Name: ftp.altlinux.org
Address: 62.152.55.238
# update-kernel
Running kernel version: kernel-image-std-def-1:4.4.86-alt0.M80C.1
Checking for available kernel packages...
Latest kernel std-def-1:4.4.86-alt0.M80C.1 is already running on your system.
No upgrade is needed. Use -f for force.
# apt-get -u upgrade
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages will be upgraded
certmonger libgnutls30
The following packages have been kept back
efibootmgr glibc-core glibc-gconv-modules glibc-locales glibc-nss glibc-pthread glibc-timezones glibc-utils guile18 i586-glibc-core.32bit iconv libipa_hbac libldb
libnetapi libnss-myhostname libpam0 libpasswdqc libpolkit libpython libsmbclient libsss_certmap libsss_idmap libsss_nss_idmap libtalloc libtevent libwbclient nscd
ntp-utils ntpdate ntpq openssh-clients openssh-common openssh-server pam pam0_passwdqc pam_systemd passwdqc-utils perl-base perl-devel perl-threads polkit ppp
python python-base python-dev python-module-cryptography python-module-ipa_hbac python-modules python-modules-bsddb python-modules-compiler python-modules-ctypes
python-modules-curses python-modules-email python-modules-encodings python-modules-hotshot python-modules-json python-modules-logging python-modules-multiprocessing
python-modules-sqlite3 python-modules-unittest python-modules-xml python-tools-2to3 python3 python3-base samba-client samba-client-libs samba-common-libs
samba-common-tools samba-libs sssd sssd-ad sssd-client sssd-ipa sssd-krb5 sssd-krb5-common sssd-pac strace systemd systemd-services systemd-utils udev udev-extras
2 upgraded, 0 newly installed, 0 removed and 82 not upgraded.
Need to get 1318kB of archives.
After unpacking 533kB of additional disk space will be used.
Do you want to continue? [Y/n] n
Abort.
Магия, не иначе) Но что делать с проблемой пока неясно.