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anyone can help me, How to write secondary ipv6 from he.net on my vps into /etc/network/interfaces?
my OS Debian 10
HE gives you an example config in the dashboard.
To add a second ip, you could use:
iface yourtunnelinterface:1 inet6 static
address your address + /ne
Maybe have a look here: https://wiki.debian.org/NetworkConfiguration