[CentOS] centos 6.3 ipv6 default gateway

hello,
   i met a problem in configuratiion of ipv6 gw in my box
i install centos 6.3 (64 bit) on my boxs, which have four netcard.
i use a straight-through cable to connect centosv0:netcard-2 and
centosv1:netcard2
the topology is this:
client c(windows xp) <-->centosv0:netcard-3 <--> centosv0:netcard-2 <--->
centosv1:netcard-2 <---->centosv1:netcard-2  <---> client d (backtrack r2
32)
1:2:3:4::2/64          1:2:3:4::1/64                       1:2:3::4/64
                  1:2:3::5/64             1:2:3:5::1/64
 1:2:3:5::2/64

what i want to do is set default gw on centosv0 to centosv1

i configure /etc/sysconfig/network-scripts/ifconfig-eth2  (centosv0) as this
DEVICE="eth2"
BOOTPROTO=static
HWADDR="60:A4:4C:23:2F:6F"
NM_CONTROLLED="yes"
ONBOOT="yes"
TYPE="Ethernet"
#UUID="0ddcf499-878f-4ac7-9d1a-c27f85d2bccf"
IPV6INIT=yes
IPV6ADDR=1:2:3::4
IPV6_DEFAULTGW=1:2:3::5

and i also configure /etc/sysconfig/network to this:
NETWORKING=yes
HOSTNAME=centosv0
NETWORKING_IPV6=yes
IPV6_AUTOCONF=no

but i met an error:
Bringing up interface eth2:  WARN     : [ipv6_add_route] Unknown error

i do not know how why,and can some one gives me some suggestion?
thanks a lot.