eth0 show "failed to bring up " on static address but not on dhcp

hi all,
i am struggling to bring up eth0 on static address.
my /etc/network/interfaces is look like :

auto lo
iface lo inet loopback

iface eth0 inet6 static
address 2001:468::3
netmask 64
auto eth0

#ifconfig
show error :Failed to bring up eth0.

but when i change /etc/network/interface file like this:

auto lo
iface lo inet loopback

iface eth0 inet dhcp

auto eth0


then it doesn't show any error and getting internet on eth0.
plz help me.......

you need to specify the gateway and nameservers as well

Code:

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gateway <ip>
dns-nameserver <ip>

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