On Juniper SRX devices, operators may observe that ICMP packets are visible when using monitor traffic interface fxp0 matching icmp, but no ICMP packets appear when monitoring a revenue interface (for example, ge-0/0/0, reth0, etc.).

This is expected behavior when pinging a revenue interface; the ICMP traffic is processed entirely by the Packet Forwarding Engine rather than the Routing Engine, and therefore does not appear in the monitor output.