This article goes over the bindings being stuck in "Selecting" when the Junos device is working as DHCP Server.

example@junos> show dhcp server binding

IP address Session Id Hardware address Expires State Interface

10.10.10.1 004 aa:bb:cc:dd:ee:ff 86329 SELECTING ge-0/0/0.0

• Binding stuck in "Selecting"
• If "monitor traffic" command is used, the SRX can be seen sending an Offer packet in response to the end device's Discover, but the end device does not respond back.

The binding being stuck in "selecting" means the SRX sent the Offer message and has not received a Request message yet.

This can happen for multiple reasons, and the burden of the issue is not on the SRX device as not receiving any Request from the client.

For troubleshooting a PCAP can be done, as one of the possible causes is a second DHCP Server in the Broadcast Domain, the end device will send the Request to that other DHCP server, and the Offer from the other DHCP server will be seen in the PCAP being a Broadcast packet.

https://supportportal.juniper.net/s/article/Includes-video-How-to-create-a-PCAP-packet-capture-on-a-SRX-branch-device

https://supportportal.juniper.net/s/article/SRX-Example-Creating-a-PCAP-packet-capture-on-high-end-SRX-devices?language=en_US