6to4 настраиваю подобно:
### interfaces -*- Default-Generic -*-
## Basic 6to4 tunnel setup example
auto 6to4
iface 6to4 inet6 v4tunnel
## IPv4 address: 192.0.2.34
## $ printf 2002:%x%02x:%x%02x::1\\n 192 0 2 34
address 2002:c000:222::1
netmask 16
local 192.0.2.34
endpoint 0.0.0.0
## Use the following 6to4 gateway (anycast) if it works
gateway ::192.88.99.1
## Use an HE.NET router if it doesn't
# gateway ::216.66.80.98
post-up ip route add unreachable "$IF_ADDRESS"/48
## AIUI, IPv6 forwarding cannot be enabled on a per-interface basis
# post-up sysctl -w net.ipv6.conf."$IFACE".forwarding=1
### interfaces ends here
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