1- on the SRX: DHCP Client:
root@srx300-3> show system services dhcp client
...
root@srx300-3> request system services dhcp release ge-0/0/0.0
2- On the server:
root@EX4200_TOR_SELab> show configuration | display set | match traceoptions
set system processes dhcp-service traceoptions file jlkdhcp_logfile
set system processes dhcp-service traceoptions flag all
%tail -F /var/log/jlkdhcp_logfile