Proxmox 5.0-32: how to use default IPv4?

Question

linux

Greetings. Such a problem: after updating Proxmox to version 5.0-32 (and Debian, respectively, from 8 to 9.1), all connections go through IPv6 by default

# ping ya.ru
PING ya.ru(ya.ru (2a02:6b8::2:242)) 56 data bytes

Because of this, in particular, I cannot do

# pveam update

From virtualok connections go normally, as before.
How to fix?

Answer 1

add to /etc/sysctl.conf

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

run:
check:
Should output 1
reboot

Answer 2

remove config for ipv6 from network