This article explains how SRX can be configured to forward the DHCP binding logs to an external syslog server.

SRX is acting as a DHCP server but it does not forward the DHCP binding logs to the syslog server.

You can enable logging for DHCP process while SRX is acting as the DHP server using the below given command:

User@srx> configure

User@srx# set system processes dhcp-service log session server

User@srx# commit

This will enable logging for DHCP and you can create a syslog file to save these and send these to an external syslog server as explained in the below given tech doc:

https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/dhcp-service-log-edit-systems.html#:~:text=Enable%20DHCP%20session%20log%20on%20the%20device.,session%20logs%20for%20monitoring%20and%20troubleshooting%20purposes