ipv6ip / 6in4 tunnels Ubuntu

Add the following to your /etc/network/interfaces file
———–
auto tun0
iface tun0 inet6 v4tunnel
    address <Tunnel IPv6 Address>
    netmask <IPv6 Subnet Mask>
    endpoint <IPv4 Address of Tunnel Server>
    ttl 255
    up ip link set mtu 1480 dev tun0
    up ip route add ::/0 dev tun0
———–
The local tunnel endpoint will be the IPv4 address of the interface facing the Tunnel Server. You may need to reduce the MTU although PMTU happens automatically. You can use tracepath6 ipv6.google.com to find the lowest MTU in your path.

Also make sure you add the following to your IPv4 IPtables rules:

-A INPUT -s <IPv4 Address of Tunnel Server> -i <WAN interface> -j ACCEPT

IPv6 on Cisco with Snap

DHCPCLIENT#show running-config

version 12.4
!
hostname DHCPCLIENT
!
ipv6 unicast-routing
!
interface Serial0/0
no ip address
ipv6 address autoconfig default

!--- The autoconfig default adds a static ipv6 
!--- default route pointing to upstream DHCP server.

!
ipv6 enable
ipv6 dhcp client pd prefix-from-provider

!--- The DHCP client prefix delegation is 
!--- given the name prefix-from-provider.

!
clock rate 2000000
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
ipv6 address prefix-from-provider ::1:0:0:0:1/64

!--- The first 48 bits are imported from the delegated
!--- prefix (2001:db8:1200) and the ::/64 is the client
!--- identifier that gives the interface Fa0/1 the
!--- global IPv6 address 2001:DB8:1200:1::1/64.

!
ipv6 enable
!
interface FastEthernet0/1
no ip address
duplex auto
speed auto
ipv6 enable
ipv6 address prefix-from-provider ::1/64

!--- Similarly, the global IPv6 address 
!--- for fa0/1 is 2001:DB8:1200::1.

!
end