Diagnostics

Apply a structured troubleshooting method, use debug flow and the session table, capture packets, and isolate where traffic is dropped.

Troubleshoot layer by layer, from the bottom up: confirm physical/interface status, then ARP/L2, then routing (is there a route, correct next hop?), then the firewall policy match, then NAT, then security profiles. Isolating which stage fails prevents guesswork.

get system status
get system interface physical
execute ping 
execute traceroute

What is the recommended general approach to troubleshooting a traffic problem?