If you want to capture some icmp traffic destined for a Junos router by using “monitor traffic“, you must re-think what you are doing. For example you issued the following command and you started ping from another host towards this Junos router.
admin@host> monitor traffic interface ge-0/0/1 matching "icmp or tcp"
verbose output suppressed, use <detail> or <extensive> for full protocol decode
Address resolution is ON. Use <no-resolve> to avoid any reverse lookup delay.
Address resolution timeout is 4s.
Listening on ge-0/0/1, capture size 96 bytes
Unfortunately you won’t get any icmp request on this capture. The underlying reason that I know is that ICMP responses are handled by the data plane (PFE) instead of the control plane. In other words, you don’t really receive this traffic and PFE responds to this ICMP.
What I do usually is to create a sample TCP traffic (e.g SSH request) towards the RE to see some packet traffic.