This article explores the scenario when IPv6 ping is not working but the ARP leaning of the farend device is working

root> show ipv6 neighbors interface ae24.0

IPv6 Address Linklayer Address State Exp Rtr Secure Interface

2402:abcd:0:2::651 7c:f8:80:70:60:50 reachable 7 yes no ae24.0

fe80::7ef8:ff80:fe50:5cdd 7c:f8:80:70:60:50stale 128 yes no ae24.0

root> ping 2402:abcd:0:2::651

PING 2402:abcd:0:2::651 56 data bytes

^C

--- 2402:7800:0:2::651 ping statistics ---

4 packets transmitted, 0 received, 100% packet loss, time 3080ms

Step-1: Check the configuration on both the sides. Check the subnet mask if it falls in the same network.

Step-2: Check for any firewall filter applied which is blocking ICMPv6. Remove all filters and check for ping again.

Step-3: Check if the far-end device MAC is getting learnt. If yes, then ARP is being sent and received on the interface.

Step-4: The only option is then that it could be a PFE level corruption. Or a PFE related programming issues.

Step-5: To solve this, deactivate the family inet6 of the interface and then activate it.

Step-6: If the issue persists, then deactivate/activate the interface.

Step-7: FPC reboot, and router reboot can also be considered as a last resort.