The SRX300 (and SRX550M) are configured to drop IPv6 traffic by default: see documentation: When IPv6 is configured on SRX300 Series and the SRX550M devices, the default behavior is set to drop mode because of memory constraints.https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/ipv6-flow-processing-enabling.html This can be confirmed: admin@CS7-HQ-FW02> show security flow status Flow forwarding mode: Inet forwarding mode: flow based Inet6... Continue Reading →