Hi Alex, thanks for the reply. Yes it does receive ARP requests:
09:49:37.170221 bpf_flags 0x81, In
Juniper PCAP Flags [Ext, In], PCAP Extension(s) total length 16
Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
Device Interface Index Extension TLV #1, length 2, value: 32768
Logical Interface Index Extension TLV #4, length 4, value: 67
-----original packet-----
00:c0:89:1b:04:c3 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: arp who-has 109.3.4.88 tell 217.2.1.81
09:49:37.180074 bpf_flags 0x81, In
Juniper PCAP Flags [Ext, In], PCAP Extension(s) total length 16
Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
Device Interface Index Extension TLV #1, length 2, value: 32768
Logical Interface Index Extension TLV #4, length 4, value: 67
-----original packet-----
00:c0:89:1b:04:c3 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: arp who-has 109.3.4.88 tell 217.2.1.81
(The upstream router has multiple IP addresses: 109.3.4.65 and 217.2.1.81.)
I'm in the process of capturing an ARP request from the upstream router for 109.3.4.92 because this does work and it would be good to compare the two. However, the upstream router has a 4-hour ARP cache (I think), so it might be a bit of a wait!
Cheers
Mark
EDIT: Still waiting, but this may be relevant when looking at the routing table:
109.3.4.88/32 *[Static/1] 1d 17:18:27
Discard
109.3.4.92/32 *[Local/0] 1d 17:18:47
Local via reth0.0
From what I've read, it is normal now for the SRX to set the ProxyARP address with a Discard route. https://kb.juniper.net/InfoCenter/index?page=content&id=KB24709&smlogin=true
The arcticle states that nevertheless if there is a valid ProxyARP entry, ARP reply will be send. So, I think that the "Discard" in the routing table is not relavant to this problem?