calico: can not ping6 to ipv6 address of pod

In my K8S cluster of verison 1.16 , with just IPv4 stack on , I run the calico of version 3.9.0. I create a default ipv4 ipPool and a default ipv6 ipPool . then, I create a pod owning an ipv4 and an ipv6 address

3: eth0@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1480 qdisc noqueue state UP group default 
    link/ether 66:32:71:b9:a8:f1 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.28.156.7/32 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fc00::10:4511:66bb:a4e2:9c06/128 scope global 
       valid_lft forever preferred_lft forever

From another node , I failed to ping6 the pod ip fc00::10:4511:66bb:a4e2:9c06 . Finally, I found the reason is that the IPv6 route on the pod’s node is gone , like "fc00::10:4511:66bb:a4e2:9c06 via calicoXXXX " . I try to add this route manually, it succeeded to ping6 from another node . The strange is that the route that I added manually disappears after about 30 seconds. So, I guess something remove the pod’s ipv6 route on the node , which makes the node failed to forward packets to the pod .

BTW, the following sysctl config has been checked:

net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.dce.accept_ra = 0
net.ipv6.conf.all.disable_ipv6 = 0

I also did other 2 test case:

1. when the calico on , I add the route by manual , like “fc00::10:4511:66bb:a4e2:9c06 via ens192” , the route will not disapear. 2 when the calico removed, I add the route by manual , like “fc00::10:4511:66bb:a4e2:9c06 via calicXXXX” , the route will not disapear.

So , I guess this is related to calico-node , After checking the bird6 config on the calico-node, I still do not figure out .

Anyone has an idear , thx

Your Environment

• Calico version 3.9.0

• Orchestrator version (e.g. kubernetes, mesos, rkt): k8s 1.16.0 docker 18.09

• Operating System and version: centos 7.6

• Link to your project (optional):