IPv6 ping fails from ipv6 network namespace to VM using ip netns command and its getting dropped in table 55

Steps followed:

1 Used ODL Build boron -SR4 build.(distribution-karaf-0.5.4-20170410.154811-55.tar.gz )
2.Created IPv6 network and subnets
and associated subnet to router .
3.Spawned the VM with default security group.
4.while pinging from ipv6 network namspace to VM ipv6 address and its getting dropped at table=55.

root@ubuntu-227:/opt/stack/devstack# sudo ip netns exec qdhcp-9071433b-7ad4-4170-9770-7d0278191ca0 ping6 2001:db8:5678:0:f816:3eff:fe8d:a7a1
PING 2001:db8:5678:0:f816:3eff:fe8d:a7a1(2001:db8:5678:0:f816:3eff:fe8d:a7a1) 56 data bytes
^C
— 2001:db8:5678:0:f816:3eff:fe8d:a7a1 ping statistics —
2 packets transmitted, 0 received, 100% packet loss, time 1007ms