# setenforce to 'Permissive' if default enforce is 'Enforcing'
setenforce 0

# create namespace
ip netns add hidden

# Active ::1 inside namespace
ip netns exec hidden ip link set dev lo up

# Add bridge inside 'hidden' namespace and turn on
ip netns exec hidden brctl addbr hiddenbr0
ip netns exec hidden ip link set dev hiddenbr0 up

# Add virtual patch cables to bridge
ip link add eno1 type veth peer name eno1-port
ip link set eno1-port netns hidden up
ip netns exec hidden brctl addif hiddenbr0 eno1-port

# Attach virtual patch cable to bridge and assign its far side address
ip netns exec hidden ip link add inside0 type veth peer name inside0-port
ip netns exec hidden brctl addif hiddenbr0 inside0-port
ip netns exec hidden ip link set inside0-port up
ip netns exec hidden ip link set inside0 up
ip netns exec hidden ip addr add 192.168.0.254/24 dev inside0
ip netns exec hidden ip addr add fddb:fe2a:ab1e::c0a8:00fe/64 dev inside0

# setenforce to 'Enforcing'
setenforce 1

# ip link
# nmcli con show

# nmcli connection add con-name eno1 type ethernet ifname eno1
Connection 'eno1' (b5ce0f55-6e21-4529-8096-f5bbfcc11605) successfully added.
# nmcli connection show | grep eno1
eno1    b5ce0f55-6e21-4529-8096-f5bbfcc11605  802-3-ethernet  --
# ip addr show eno1
6: eno1@if5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether fe:70:83:fc:2e:d3 brd ff:ff:ff:ff:ff:ff link-netnsid 0

# nmcli connection show eno1 | grep ipv6
ipv6.method:                            auto
ipv6.dns:                               --
ipv6.dns-search:                        --
ipv6.dns-options:                       (default)
ipv6.dns-priority:                      0
ipv6.addresses:                         --
ipv6.gateway:                           --
ipv6.routes:                            --
ipv6.route-metric:                      -1
ipv6.ignore-auto-routes:                no
ipv6.ignore-auto-dns:                   no
ipv6.never-default:                     no
ipv6.may-fail:                          yes
ipv6.ip6-privacy:                       -1 (unknown)
ipv6.addr-gen-mode:                     stable-privacy
ipv6.dhcp-send-hostname:                yes
ipv6.dhcp-hostname:                     --
ipv6.token:                             --

# nmcli con mod eno1 ipv6.addresses 'fddb:fe2a:ab1e::c0a8:1/64 fddb:fe2a:ab1e::c0a8:fe'
# nmcli con mod eno1 ipv6.method manual
# nmcli con down eno1
# nmcli con up eno1

# ping6 fddb:fe2a:ab1e::c0a8:1
# ping6 fddb:fe2a:ab1e::c0a8:fe

# ip -6 route

# ping6 ff02::1%eno1