In Juniper high availability (HA) SRX Series device implementations, which interface will be used to...

The correct answer is A. fab. In SRX Series chassis clustering, the fabric interface, shown as fab0/fab1, is the data-plane HA link used between cluster nodes. Juniper states that SRX chassis clusters use the fabric interface for session synchronization and traffic forwarding, and that the fabric link synchronizes dynamic runtime state, including session-state objects created by NAT, ALG, authentication, and IPsec processing. This is what enables stateful failover and session continuity when traffic processing moves between nodes.

Option B, fxp0, is wrong because fxp0 is the out-of-band management interface, not the chassis-cluster synchronization path. Option C, fxp1, is tempting but wrong for this question: fxp1 is the control-link interface used for control-plane cluster functions such as heartbeats and cluster control communication, not the main session-state synchronization path. Option D, swfab, is not the standard SRX chassis-cluster fabric interface name used for this function. Juniper’s clustering configuration examples specifically define fab0 and fab1 as the interfaces used for the fabric connection and data-plane RTO/session synchronization.