[CentOS] how to capture packets that was forwarded

hello,
the topology is like this:

 centos v0:eth1 <------> centos v0: eth2
  fc00:2:3:4::1                      fc00:2:3::4

i turned the packet forwarding

ping6 -i eth2 fc00:2:3:4::1
the output is

PING fc00:2:3:4::1(fc00:2:3:4::1) from fc00:2:3::5 eth2: 56 data bytes
>From fc00:2:3::4 icmp_seq=1 Destination unreachable: Administratively
prohibited
>From fc00:2:3::4 icmp_seq=2 Destination unreachable: Administratively
prohibited
>From fc00:2:3::4 icmp_seq=3 Destination unreachable: Administratively
prohibited
>From fc00:2:3::4 icmp_seq=4 Destination unreachable: Administratively
prohibited

why the box do not forwarding icmp packets to eth2?
and how to set forwarding rules on centos 6.3?
Thanks