Cannot ping internal IPv6 addresses of VM instances in Google Cloud

pa flag

I'm testing a connection between two VM instances in the same subnet. The VPC has enabled dual stack with internal IPv6 addresses and both VMs received a IPv6 Unique Local Address. The VMs cannot ping eachother via ICMPv6 while it works with ICMPv4.

I've added the following firewall rules to be sure that nothing gets denied.

Name Type Destination Filter Protocols/Ports Action
ipv6-in Egress Apply to all ::/0 all Allow
ipv6-out Ingress Apply to all ::/0 all Allow

Logs have been enabled for both rules but there are no entries. What exactly am I doing wrong? Do I have to configure a route?

Edit: I set the priority of the rule to 65535, the highest possible number. However, the higher the number, the lower the priority is. The IPv6 connectivity and ICMPv6 work now after setting it to 1000.

John Hanley avatar
cn flag
1) Show the command and output. 2) Go to the Google Cloud web GUI -> Compute Engine -> VM Instances. Are you using the IPv6 address as shown? 3) Google Cloud has VPC Firewalls. That means you can consider disabling OS level firewalls. One reason is that the VPC Firewall will prevent unwanted traffic from reaching your instance saving your money and CPU resources.
LaurentD avatar
pa flag
@JohnHanley Found the mistake... I set the priority to 65535 because I saw the default VPC having the IPv4 firewall rule 'default-allow-internal' with priority 65534 and thought I had to put the highest number for the IPv6 rule, in this case 65535. However, the lower the number, the higher the priority is. I've changed it to 1000 and it works now. I should have put a screenshot of the entire rule instead of only a subset. Thanks for the help.
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