And here's traffic monitor output:
por@rt-fw1> ...or traffic interface fe-0/0/7 size 1500 detail no-resolve
Address resolution is OFF.
Listening on fe-0/0/7, capture size 1500 bytes
22:11:20.117617 Out IP (tos 0x0, ttl 1, id 17287, offset 0, flags [none], proto: UDP (17), length: 279) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 251, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
Lease-Time Option 51, length 4: 86400
22:11:20.145938 In IP (tos 0xc0, ttl 1, id 19443, offset 0, flags [none], proto: UDP (17), length: 318) 87.100.128.1.67 > 255.255.255.255.68: BOOTP/DHCP, Reply, length 290, xid 0x38a9997a, Flags [Broadcast]
Your-IP 87.100.164.244
Gateway-IP 87.100.128.1
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Offer
Lease-Time Option 51, length 4: 18000
RN Option 58, length 4: 9000
RB Option 59, length 4: 15750
Server-ID Option 54, length 4: 87.100.128.1
22:11:20.147160 Out IP (tos 0x0, ttl 1, id 17290, offset 0, flags [none], proto: UDP (17), length: 302) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 274, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
Server-ID Option 54, length 4: 87.100.128.1
Parameter-Request Option 55, length 9:
Default-Gateway, Lease-Time, Subnet-Mask, Domain-Name
Domain-Name-Server, TFTP, BF, Option 120
Netbios-Name-Server
Requested-IP Option 50, length 4: 87.100.164.244
DHCP-Message Option 53, length 1: Request
Lease-Time Option 51, length 4: 86400
22:11:24.148684 Out IP (tos 0x0, ttl 1, id 17311, offset 0, flags [none], proto: UDP (17), length: 302) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 274, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
Server-ID Option 54, length 4: 87.100.128.1
Parameter-Request Option 55, length 9:
Default-Gateway, Lease-Time, Subnet-Mask, Domain-Name
Domain-Name-Server, TFTP, BF, Option 120
Netbios-Name-Server
Requested-IP Option 50, length 4: 87.100.164.244
DHCP-Message Option 53, length 1: Request
Lease-Time Option 51, length 4: 86400
22:11:32.150387 Out IP (tos 0x0, ttl 1, id 17333, offset 0, flags [none], proto: UDP (17), length: 302) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 274, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
Server-ID Option 54, length 4: 87.100.128.1
Parameter-Request Option 55, length 9:
Default-Gateway, Lease-Time, Subnet-Mask, Domain-Name
Domain-Name-Server, TFTP, BF, Option 120
Netbios-Name-Server
Requested-IP Option 50, length 4: 87.100.164.244
DHCP-Message Option 53, length 1: Request
Lease-Time Option 51, length 4: 86400
22:11:48.152282 Out IP (tos 0x0, ttl 1, id 17389, offset 0, flags [none], proto: UDP (17), length: 302) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 274, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
Server-ID Option 54, length 4: 87.100.128.1
Parameter-Request Option 55, length 9:
Default-Gateway, Lease-Time, Subnet-Mask, Domain-Name
Domain-Name-Server, TFTP, BF, Option 120
Netbios-Name-Server
Requested-IP Option 50, length 4: 87.100.164.244
DHCP-Message Option 53, length 1: Request
Lease-Time Option 51, length 4: 86400
22:12:20.154359 Out IP (tos 0x0, ttl 1, id 17483, offset 0, flags [none], proto: UDP (17), length: 302) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 40:b4:f0:57:e9:47, length 274, xid 0x38a9997a, Flags [Broadcast]
Client-Ethernet-Address 40:b4:f0:57:e9:47
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
Server-ID Option 54, length 4: 87.100.128.1
Parameter-Request Option 55, length 9:
Default-Gateway, Lease-Time, Subnet-Mask, Domain-Name
Domain-Name-Server, TFTP, BF, Option 120
Netbios-Name-Server
Requested-IP Option 50, length 4: 87.100.164.244
DHCP-Message Option 53, length 1: Request
Lease-Time Option 51, length 4: 86400
Which seems as if the DHCP server would never acknowledge the request for an address, but at least two other devices in the same network get the address without a problem. Which makes me think that maybe SRX doesn't see the ack for some reason that beats me.